Firefox Configuration Guide for Privacy Freaks and Performance Buffs


See the revision history at the end for a list of changes.

Before embarking on this journey into the bowels of Firefox, you may want to first read, Tor verses a VPN – Which is right for you?. If you choose to use the Tor Browser, you need not digest this guide.


This guide is long, boring, dry, tedious and somewhat technical, so if you don't feel comfortable digesting it, try the The Firefox Privacy Guide For Dummies! instead, however be aware that it doesn't offer the same degree of protection.

To understand my personal position regarding the ethical nature of the Mozilla Foundation, read The Mozilla Monster.

WARNING: This guide is not for use with the Tor browser. Configuring the Tor browser as outlined in this guide will result in potentially serious risks to your privacy.

Though this guide is centered around the Firefox web browser, users of other browsers, email clients and Mozilla products may find it useful. If you are interested in hardening the Thunderbird email client, see the ghacks-thunderbird-user.js repository by 'dngray' as well as my Thunderbird user.js repository.

Many of us are aware of the immense threats to our line privacy and security posed by various technology companies, governments and malicious hackers, any of which may go to great lengths to monitor our electronic communications. Governments and their "intelligence" apparatuses not only spy on each other, but on the citizenry as well and they leverage the services of various companies to do so, including Microsoft, Google, Facebook, Verizon, Comcast, Amdocs as well as many others. While the data these companies collect may be used for relatively benign purposes such as targeted advertising, the intentions are often far more sinister. Much of what Edward Snowden has brought to light is not new, but it seems the information has been presented in a way that has captured the attention of the public, prompting many to seek ways to mitigating the threats.

While the primary goal of this guide is to help the reader thwart some of the more obvious efforts to track and profile us as we surf the web, as well as increase browser security and performance, understand that i am not an expert in computer security or privacy and there are surely many more variables and vectors for attack than i am aware of. While there are many known methods that can be used to compromise our digital well being, how many more are there of which we know nothing? Or what about techniques that most of us never consider? For example, even if you are a knowledgeable, technically proficient and privacy conscious individual who uses open hardware devices running open source software and a security enhanced operating system, and even if you connect to the internet only through Tor, you may still be at risk of being tracked because, disregarding everything else, your unique writing style can be used to identify you. It is not this level of sophistication that i will attempt to address here however. My goal is to share what i have learned over the years as a casual web surfer and computer user who has a hobbyist-grade interest in computer security and digital privacy. Having said that, i believe — and please correct me if i'm wrong — this guide is currently one of the more comprehensive of its kind in that it addresses many aspects of the Firefox browser including configuration and extensions as well as other optimizations. If you want to go further than this guide can carry you, see the resources section at the end which includes the fine article, Improve Your Privacy in the Age of Mass Surveillance. I would also highly recommend using a VPN to help prevent spying by your ISP or other actors. That One Privacy Site is also an excellent resource, as is TorrentFreak which publishes annual reports regarding many of the popular VPN service providers. Their 2018 report is here.

As with any modern, mainstream web browser, Mozilla Firefox is a highly complex beast consisting of millions of lines of code and hundreds of configuration options, many of which are interlinked, hidden, or undocumented. Things can go down the toilet real fast if you start messing around with its settings willy-nilly and poorly coded add-ons can compound the problem. Here we will attempt to accomplish our goals in an efficient manner with a minimal dependency upon carefully chosen browser extensions, or add-ons.

A bit of a trade-off must be expected when we tighten security and privacy insomuch as some websites will cease to function properly until the settings for those specific sites are adjusted. Anyone who has used a content filter such as NoScript or Request Policy will understand that certain resources must be allowed for a given website to function in an acceptable way. Similar to NoScript however, the process of allowing required resources usually consists of a mouse click or three followed by a page refresh and once we have made the necessary adjustments for our favorite websites, our workload will be greatly reduced. Nevertheless, be prepared to put a little more effort into your web surfing activities in general and expect the occasional hard-case where more fiddling than usual will be required to get a particular site working properly. The pay-off is a much cleaner and faster web that is less able to track and profile us, as well as a somewhat hardened and speedier Firefox that is more resistant to attack.


Add-on/extension: I use these terms interchangeably. A web browser add-on or extension is a piece of software typically developed by a 3rd party that extends the capability of the browser. Web extensions, which leverage the WebExtension API (Application Programming Interface), have replaced the older legacy (XUL/XPCOM) extensions beginning with Firefox version 57. This newer type is essentially the same format as used by Google Chrome and other web browsers. Unfortunately the WebExtension API is severely limited. For example, such extensions cannot modify the GUI (Graphic User Interface) of Firefox in the same way legacy extensions could.

AMO:, the Mozilla Add-ons website.

Browser fingerprinting: Web servers can employ a wide variety of methods to uniquely identify your web browser, hardware and software configuration, collectively known as fingerprinting. Fingerprint data may consist of many bits of information about your environment which, when combined, can be used to uniquely identify a web browser. This information may include such things as the browser viewport dimensions, installed add-ons, its capabilities, your locale, your operating system, querying the browser cache, your display resolution and much more. This information can be gleaned using various techniques, including through HTTP header information, JavaScript, and others, and it is often used for the purpose of tracking and profiling the user and their web activities. For further information, see A Primer on Information Theory and Privacy and Panopticlick. See also the explanation for 'tracking' and 'web storage' below.

Crapware/malware: I consider crapware/malware to be software which contains code which is not relevant to the functionality users expect. As such the term crapware, or malware, refers largely to adware, tracking code and other malicious code with regard to web browser extensions. Crapware is often added to browser extensions by a company or solo developer who wishes to monetize their work and often takes the form of profiling users and selling the data collected by the extension to a marketing company, however much worse is possible.

CDN: A Content Delivery Network is a service that hosts reusable content, such as graphics and reusable scripts which developers can leverage to make building web platforms easier. CDNs often present a threat to our privacy by tracking our web activities. They are perhaps a most formidable threat because a single CDN service may be used by many millions of popular websites and therefore the spying capabilities of the company providing the CDN service can be widespread and cross-domain in nature. The use of CDNs is prolific today and since many websites will not function without the content they deliver, globally blocking CDN content is hardly an option.

CSS: Cascading Style Sheets are used primarily to apply visual styling to HTML elements, thus making web pages look pretty, however the capability of CSS has been expanded well beyond its original specifications to the point where it can now be used for nefarious purposes.

Domain/subdomain/TLD: In the example '', 'example' is the root domain, 'sub' is a subdomain of the root domain and 'com' is the TLD, or Top Level Domain. You can think of root domains and subdomains as sort of different containers which are used to separate content for a single website. For example, let's say is focused primarily on information about kittens, but they also might have a web store where they sell paper bags. In order to keep the store content separate, they may host the store on the subdomain ''.

HTTP/HTTPS: Hypertext Transfer Protocol and Hypertext Transfer Protocol Secure are communication protocols used by computers to transmit data over the internet. For HTTP an insecure, unencrypted connection is established which is vulnerable to ISP (Internet Service Provider) snooping and man-in-the-middle attacks, while a secure, encrypted connection is established with HTTPS. Some web servers simply do not support HTTPS and for this reason i will again point out the necessity of using a VPN.

JavaScript (JS): A powerful programming language that runs code within the browser, often to make pages interactive. Although JavaScript is used by many websites for legitimate reasons, it can and often is used maliciously to perform a wide variety of attacks against the browser and our privacy. Many browser fingerprinting/tracking techniques depend on JavaScript being enabled and this is the default in every mainstream web browser.

Tracking: Once the identity of the browser is known through fingerprinting, it is then possible to track its activity both within the same domain and across domains. See also the explanation for 'web storage' below.

Web fonts/remote fonts: These are font packages typically hosted by a 3rd party, such as Google, which a web developer may use to specify how text is displayed on a website. Web fonts present a few problems regarding browser tracking and security.

Web server: For the purpose of this document, a web server is a computer that is connected to the internet which hosts (serves) one or more websites.

Web storage: In addition to HTTP cookies and web caching, most/all popular web browsers also allow a web server to store data locally using several storage methods including local and session storage, indexedDB storage, storage, Etag cache storage, Local Shared Objects storage, Service Workers, offline storage, HTTP Strict Transport Security storage and other methods. Stored data for Firefox may consume up to 50% of your free disk space. If you are concerned about protecting your privacy, you have far more to worry about than the simple text cookies of yesteryear which in theory, but not always in practice, could be read only by the domain that set them and this problem only seems to worsen as the web grown more complex.


Code editor

You will need a decent code editor with syntax highlighting to edit Firefox's configuration files. Linux users should have something suitable installed by default, however if you're running Windows i might suggest Notepad++ or PSPad, the latter being the simpler of the two.

Unhide file extensions

If Windows is using you, the geniuses at Microsoft have taken it upon themselves to hide file extensions from the user. You will need to un-do that.

Getting Firefox

Though i recommend using the stable release version of Firefox, there are other versions such as the ESR (Extended Support Release), however it is usually an older version. There is also a Developer Edition which includes the very latest features (and bugs). While there are many 3rd party forks of Firefox, including Waterfox, Cyberfox, Pale Moon (or Basilisk from the same developer), etc., i do not recommend using any of them. The small development teams for these 3rd party builds often lag far behind regarding security patches and they can be buggy and incompatible with the latest add-ons (Pale Moon doesn't support the newer Web Extensions at all). While some forks may be more privacy-centric out of the box, we can accomplish essentially the same degree of privacy or better with the official Mozilla release version.

The user.js file

The user.js file is typically where your personal Firefox preferences are best kept, however in our case we will be using a preconfigured one and then storing our personal preferences in a user-overrides,js file which will be appended to user.js using a script.

The user.js file we will use is a result of a formidable effort by 'pants' and the rest of the 'ghacks-user.js' crew and contributors. Their work became rather popular when it was published as A comprehensive list of Firefox privacy and security settings by Martin Brinkmann on The project has since moved GitHub, but don't download anything just yet.

Firefox post install cleanup

After installing Firefox, and before you make any changes, back-up your current profile. If you don't know where it is, enter about:profiles in the address bar and click the 'Open Directory' button in the 'Root Directory' row. The easiest way to backup your profile is to select your profile folder under the /firefox directory and press Ctrl+C to copy the folder, then Ctrl+V to paste it in the same place but with a different name. I might suggest keeping the original name and just appending -bak to the copy. From this point on, all changes should be made to your original profile, leaving your backup profile untouched in case something explodes. Next, delete everything from your original profile, keeping only your bookmarks and whatever else you need. See the article Profiles – Where Firefox stores your bookmarks, passwords and other user data if you need help with what data is stored in which file/folder.

System add-ons

Packaged with Firefox are a bunch of system add-ons which are installed without your consent and they are essentially hidden (they are not listed in about:addons). Some of these add-ons have been and may currently be used for controversial purposes such as collecting data about how users interact with search engines, the browser, etc.. I suggest removing all of them. On Linux these add-ons may be found at /usr/lib/firefox/browser/features and for Windows in \Program Files (x86)\Firefox\browser\features or \Program Files\Firefox\browser\features. You can delete them in Linux using the terminal:

cd /usr/lib/firefox/browser/features
sudo rm *.xpi

These system add-ons will be reinstalled each time Firefox is upgraded. On Windows you can apparently use CCleaner to disable them. If you're running Linux with the pacman package manager (Arch, Manjaro), you can prevent their re-installation by editing the pacman configuration file, pacman.conf. Note that this will not work using Pamac, the GUI package manager, until this bug is addressed. In my case i find it easier to just bookmark the /features folder in my file manager and run the command above each time i update Firefox.

Search engines

I recommend reading Firefox Search Engine Cautions and Recommendations which offers information about how Mozilla monetizes Firefox with the included search engine plugins and what can be done to opt out of this affiliate scheme should you so choose.

Required add-ons and settings

Following are the add-ons required for this guide and their recommended settings. All of the add-ons listed here are of the WebExtension variety, meaning most should work with Firefox versions 57 to 59 and all should work with versions 60 and up. Download and configure each add-on as you go through the list. Each of these add-ons is important so don't skip any of them with the possible exception of uMatrix.

Note that there is a serious problem with Firefox regarding Content Security Policy (CSP) which has yet to be addressed by Mozilla. The short version is that, when two or more add-ons use CSP injection to modify HTTP headers, and many do, only one will succeed. For example, both uBlock Origin and uMatrix leverage CSP, as well as other suggested add-ons here. In some cases the use of CSP can be disabled in add-on settings and i have noted this in the suggested settings. Also see the Extensions section of the 'ghacks' wiki. Please create an account at Bugzilla and vote for this issue.

Canvas Blocker by kkapsner

Description: Helps to prevent browser fingerprinting through the JavaScript canvas APIs.

Settings: Following are the most important settings. Others are optional.

  • Expert mode: enabled
  • Block mode: fake
  • Faking
    • Random number generator: non-persistent
  • Canvas API
    • Protected part of the canvas API: readout
    • Protected API features: all options enabled
  • Audio API
    • Protect audio API: enabled
    • Protected API features: all options enabled
  • History API
    • Protected API features: all options enabled
  • Window API
    • Protect window API: enabled
    • Protected API features: all options enabled
  • DOMRect API
    • Protect DOMRect API: enabled
    • Protected API features: all options enabled
  • Misc

ClearURLs by Kevin R.

Description: Strips many tracking and other (mostly) unnecessary parameters from hyperlinks, such as the utm_* tracking parameters used by Google Analytics. Unlike other similar extensions, ClearURLs uses a remotely updated list from GitLab and requires little or no interaction.

Settings: Enable the option to 'Prevent tracking injection over history API'. The rest can be left at their defaults.

CSS Exfil Protection by Mike Gualtieri

Description: Helps to prevent attackers from exploiting Cascading Style Sheets (CSS) vulnerabilities.

Settings: None.

Decentraleyes by Thomas Rientjes

Description: Helps to prevent tracking and speeds-up page loading by using local copies of common JavaScript libraries rather than fetching them from a CDN.

Settings: You can enable all of the options with the possible exception of 'Block requests for missing resources' which will break some websites.

HTTPZ by claustromaniac

Description: Attempts to force websites to use an encrypted connection (HTTPS) but will fall back to an unencrypted connection (HTTP) if the website does not support HTTPS.


  • The default settings are fine. You can disable 'Automatic mode' if you want HTTPZ to display a prompt when it tries to make an HTTPS connection and fails before it connects using HTTP.

Privacy-Oriented Origin Policy (POOP) by claustromaniac

Description: Helps to protect privacy by manipulating Cross-Origin Resource Sharing (CORS) requests.

Settings: I would recommend setting the 'Global mode' to 'aggressive' and enabling the 'Exclude root domain matches' option. If you not are using uMatrix, enable the 'Spoof cross-origin Referer' option.

Site Bleacher by wooque

Description: Automatically deletes web storage when a domain is revisited. Site Bleacher is the only add-on at this time that is capable of clearing IndexedDB storage on a domain basis so far as i am aware.

Settings: Other than a whitelist there are no settings.

Skip Redirect by Sebastian Blask

Description: Skips link redirections such as used by Google, AMO and many other companies and websites, thus helping to prevent tracking. Redirects are intermediate links, such as '' for example, that redirect the browser to a final destination.

Settings: The default settings are sufficient. You will likely have to whitelist sites that no longer work properly which Skip Redirect makes easy to do since you can copy the last skipped URL by right-clicking its toolbar icon and then adding that URL or domain to the blacklist.

A word about uBlock Origin and uMatrix

It seems a lot of people have questions and misunderstandings about these two very important add-ons. Here's some questions i frequently see and my answers to them:

Q: What's the difference between uBlock and uMatrix?
A: Although they perform similar functions in that they essentially filter content much like a software firewall, the developer tries to target two different audiences, plus they work somewhat differently. Many people think uBlock is easier to use, while uMatrix offers more granular control.

Q: Can they be used together?
A: Absolutely, but because there is overlapping functionality they need to be properly configured to work together efficiently.

Q: which one should i use?
A: Both. This guide will use uBlock Origin to handle all of the static filtering (the 3rd party filter lists used for ad blocking and such) and uMatrix to handle most of the dynamic filtering (JavaScript, cookies, frames, etc.). They were both wrapped in a single extension at one time and i think the developer unnecessarily complicated matters when he split the two, thus creating two extensions with a lot of overlapping functionality. uBO is apparently targeted toward novices, yet includes an advanced mode option which has led to confusion among many users, while uMatrix is targeted toward advanced users only. This logic makes no sense to me in practice since i find uMatrix is hardly more difficult to use than uBlock in it's advanced mode.

uBlock Origin (uBO)

Description: uBlock Origin is an excellent ad/content blocker that can use the same filter lists as Adblock Plus as well as many more. Make sure you use the original uBlock Origin by Raymond Hill and no other! Of all the add-ons listed here, uBO may be the most important. If you choose not to use uMatrix, it is important that you enable advanced mode in uBO and learn how to use its dynamic filtering capabilities.

Settings: uBlock Origin (uBO) will be used in its easy mode in order to block ads and prevent tracking by employing some of the many 3rd party static filter lists which it offers. It is essential that you read the uBlock wiki sections pertaining to the easy mode to understand how to use it properly.

uBlock open dashboardOnce uBlock Origin is installed, click its toolbar icon to reveal the main pop-up interface, then click the little settings icon to reveal the "secret" Dashboard ( i say "secret" because apparently quite a few people don't know it exists and this has caused some of them to leave nasty-grams on AMO).

The first tab in the Dashboard is the Settings tab and here are the options i recommend enabling:

  • Hide placeholders of blocked elements (optional – if you are new to content blocking, you may not want to enable this so that you can get an indication as to what was blocked)
  • Privacy:
    • enable all
  • Default behavior:
    • Disable cosmetic filtering

Do not block remote fonts. Not only will doing so uglify many websites, but this is a CSP issue. Instead i suggest adding the following to the 'My filters' tab which will allow 1st party fonts globally while blocking all 3rd party fonts except for the domains you specifically allow:

! allow 1st party fonts globally (*$font,third-party), 3rd party by domain (,|

Here's an example where two domains are allowed to load fonts from a 3rd party, each separated with a pipe character ( | ):


For more on font filtering see Blocking Web Fonts for Speed and Privacy | InfoSec.

Next we want to temporarily enable the advanced user option. Notice that a little gray gear icon appears next to it when it's enabled and clicking it will display some advanced settings. I would suggest changing the value of suspendTabsUntilReady to true. Although there is no guarantee, uBO will attempt to prevent tab loading until it is ready to handle requests. This is perhaps especially useful when you exit Firefox with open tabs and have it set to restore your previous tabs on restart. After changing that setting, go back to the Dashboard and disable the 'I am an advanced user' option since we will be leveraging the more granular control offered by uMatrix for our dynamic filtering needs.

Click the settings button again on the uBlock Origin pop-up interface and select the Filter lists tab. Here are the settings and filter lists i recommend enabling:

  • Auto-update filter lists
  • Ignore generic cosmetic filters
  • network/cosmetic filters
    • My filters​​​​​
  • Built-in:
    • uBlock filters
    • uBlock filters – Annoyances
    • uBlock filters – Badware risks (enable if you run Windows)
    • uBlock filters – Privacy
    • uBlock filters – Resource abuse (blocks many cryptocurrency mining scripts)
    • uBlock filters – Unbreak (un-breaks some websites that may be broken by other filter lists)
  • Ads:
    • Adblock Warning Removal List (hide annoying website messages warning about using an ad-blocker)
    • EasyList
  • Privacy:
    • enable all lists
  • Malware domains
    • enable all lists, especially if you use Windows
  •  Annoyances:
    • Adguard's Annoyance List
    • Fanboy's Annoyance List
  • Multipurpose:
    • Dan Pollock's hosts file
    • Peter Lowe's Ad and tracking server list
  • Custom

The custom list, nocoin.txt, is for blocking cryptominers and is hosted in the adblock-nocoin-list repository on GitHub. This list supplements the 'Resource abuse' list.

As of this writing you can find over 12 million filter lists on the FilterLists website, however i strongly advise to be very careful about what ones you add, if any. In my experience the default filter lists offered by uBO are quite sufficient and adding more will only slow things down and potentially break stuff.

If you're using the Decentraleyes add-on you should add some rules to the 'My Rules' tab in the Dashboard. I recommend doing this even when uBO is configured for 'easy' mode, as the case here. When adding the rules, be sure to remove any conflicting rules for the same domains if you have any (you won't if you're starting fresh).

All other settings are optional.

uMatrix (uM)

Description: By the same developer as uBlock Origin, uMatrix is also a powerful content blocker that provides more granular control over web requests than uBlock does. Using uMatrix is somewhat optional, however if you choose not to use it then it is important that you enable advanced mode in uBlock Origin and learn how to use its dynamic filtering capabilities.


Once uMatrix is installed, click the toolbar button and then the title bar of the pop-up to open the Dashboard.

Following are the settings i recommend enabling.

Settings, Convenience:

  • Show the number of blocked resources on the icon
  • Collapse placeholder of blacklisted elements (but not blocked elements, at least not until you become more comfortable with uM)
  • Spoof <noscript> tags when 1st-party scripts are blocked

Settings, Privacy:

Note that the three options to delete web storage are not strictly required since Site Bleacher handles this storage, however i think it's better to have the redundancy, plus they both work differently.

  • Delete blocked cookies
  • Delete non-blocked session cookies 60 minutes after the last time they have been used
  • Delete local storage content set by blocked hostnames
  • Block all hyperlink auditing attempts
  • Spoof HTTP referrer string of third-party requests

Regarding the spoofing of the browser User-Agent string, my research indicates this is essentially useless and can actually make fingerprinting the browser easier. There are other potential pitfalls with spoofing the UA as well.

On the 'My rules' tab, add the following to the 'Temporary rules' pane, then save and commit your change:

no-workers: * true

This will disable web workers which will prevent certain JS from running in the background. If a page breaks as a result, you can enable web workers on a per-site basis from the uM pop-up by clicking the vertical 3 dot icon. One resource this setting will break is videos on the website. For example, if you visit this page and allow everything for all of the Dailymotion domains, the videos will still not play until you allow web-workers, however if you want to allow web-workers globally for Dailymotion so their videos will play on all websites, it would be better to visit, play a random video, then switch uM to the global scope and allow workers for

On the 'Assets' tab, disable all of the host file filter lists, purge the caches and save your changes. It is better to use uBlock Origin to control the static filter lists since it offers many more of them by default.

Also on the 'Assets' tab, enable the 'Ruleset recipes for English websites​​​​​​​' option. On the uM toolbar pop-up you will notice a puzzle piece icon which you can use to quickly import a rule-set for a resources used by the page you're visiting if it uses a 3rd party resource and if someone has created a rule-set for that resource. For example, if you visit a page with an embedded YouTube video, you can import the rule-set for YouTube instead of creating the filters manually. You might want to switch to the global scope before doing this so that embedded YouTube videos will play on all websites.

If you're using the Decentraleyes add-on you need to add some rules to the 'My Rules' tab in the Dashboard. When adding the rules, be sure to remove any conflicting rules for the same domains if you have any (you won't if you're starting fresh).

Additional add-ons

For more possibilities regarding add-ons, see Firefox Extensions: My Picks.

Automatic add-on updates

The tl;dr version is, don't enable automatic add-on updates. The longer version follows…

Regarding automatic add-on updates which is enabled by default in Firefox, they are disabled in the 'ghacks' user.js file and i would strongly suggest keeping them disabled. Automatic checking for updates is fine and this is enabled in the 'ghacks' user.js, but we do not want Firefox to update add-ons without our explicit consent. The problem here is that developers may, at any time and without notice, monetize their add-on or sell their work to an unethical 3rd party and this often results in compromising your privacy. Examples of some currently or formerly popular add-ons which contain(ed) such crapware are Abduction, a screen capture utility, Quick Locale Switcher, a language switcher, FasterFox Lite, a largely useless utility which claims to speed-up Firefox but doesn't, BlockSite, a content blocker, Stylish, a very popular utility for changing the appearance of websites, and many, many others. Not all of these extensions contained crapware when they were first introduced which is why i strongly suggest keeping automatic add-on updates disabled and carefully reviewing the change logs, permissions and privacy policies each time an add-on update is available. For more about Firefox add-ons, see Firefox Extensions – My Picks.

Firefox configuration

This guide depends heavily on the 'ghacks' user.js configuration file which alters hundreds of important Firefox preferences related to privacy and security, thus you need not worry about manually configuring anything from the Preferences menu of Firefox other than one search setting. If you choose to not use the 'ghacks' user.js, then your job may be considerably more difficult assuming your goals are similar. Still, you may find it quite helpful to refer to the 'ghacks' user.js should you choose to start from scratch.

Search bar on navigation bar

I would suggest adding the search bar to the navigation bar and using it instead of the address bar for searches. Not only might you find it more convenient, but there are potential privacy concerns when searching from the address bar. To accomplish this, open the Firefox Preferences page, click the Search item on the left and then enable the option 'Add search bar in toolbar'.

Firefox profile in RAM

With the wide adoption of speedy Solid State Drives (SSDs), the concept of sticking the Firefox profile in RAM for performance reasons may seem obsolete, however there are still benefits in doing so. If you don't want to disable disk caching, web storage and cookies globally, and thus break a lot of websites in the process, there will be substantial read and write activity for your storage media and thus unnecessary wear and tear. Placing your Firefox profile in RAM will alleviate this, however doing so can be risky should a catastrophic failure occur, such as a power failure, which could result in data loss or corruption. Fortunately there are ways to minimize the risk. If you use Windows you're on your own since i don't, suffice to say that there exists Windows compatible software that can manage RAM disks and backup your profile to your storage media. 'Bushdoctor' provides a method in a comment left on this article. Those using most any flavor of Linux have access to a neat utility called Profile-sync-daemon (PSD) which is designed specifically for this task and it works with quite a few browsers. Check your package manager to see if it's available in your repository. To get PSD working, run man psd in a terminal or consult the guide on the Arch wiki. Setting it up was very easy in my case and it has worked flawlessly and transparently ever since.


Note that Firefox stores its web cache in a location other than the profile directory. On Linux it's kept at /home/[user]/.cache/mozilla/firefox/. Normally you would have to deal with web cache separately if you wanted to store it in RAM also, however since disk caching is completely disabled in the 'ghacks' user.js (cache is stored in memory) and the cache is dumped when you exit Firefox, you need not worry about it. If you're thinking it would be more efficient to keep the browser cache instead of having to re-download objects for websites you visit frequently, you're right, however doing so will compromise your privacy. We won't exactly be dumping all of the browser cache either since we're using the Decentraleyes add-on.

Configuration files

Keep the following hierarchy in mind as you read this section. When Firefox starts:

  1. prefs.js is read by Firefox
  2. user.js is read by Firefox – all preferences in the user.js file are copied to the prefs.js file and any preferences that are duplicated in both files are overridden by those in user.js – prefs.js is then used to generate what you see in about:config
  3. user-overrides.js is never read by Firefox but these preferences are appended to the 'ghacks' user.js with a script (preferred) or by manual copying – if using the 'ghacks' user.js this is the only file you should edit and it is where all your custom preferences should be placed – this may defy conventional knowledge, so let me be clear:

If you are going to use the 'ghacks' user.js file then you should never edit it, (nor the prefs.js file) nor should you change important settings from about:config unless you're only testing something. All of your custom preferences should be placed in your user-overrides.js file and no where else, and then appended to the 'ghacks' user.js using their script.

One reason for this is because the 'ghacks' user.js is a large file that is updated frequently and if you edit it and then update it, all your changes will be lost, whereas if you copy the preferences you want to alter from the 'ghacks' user.js to your user-overrides.js and change the values there, then updating the 'ghacks' one will be fairly painless. On the other hand, should you choose to not use the 'ghacks' user.js, then you should add your changes to your own user.js and you can ignore everything stated here about the user-overrides.js. Either way, never edit the prefs.js file directly or by way of about:config unless you're just testing something.

If you do not have a general understanding of the the user.js file, you may want to read this on the 'ghacks' wiki. You should also poke around elsewhere in the wiki for detailed information on using and maintaining their user.js file.

Obtaining and maintaining the user preferences files

In your profile folder, delete or rename your existing user.js file if you have one. You can transfer any needed settings later if they are not already covered in the 'ghacks' one. Next i would suggest downloading the user-overrides.js file from my labwrat/Firefox-user.js GitLab repository by clicking the file name:

GitLab - DL file 1 of 2

… then the little cloud-looking icon:

GitLab - DL file 2 of 2

Place the file in your profile directory and then open it using your code editor and carefully follow the instructions within.

Next we want the 'ghacks' user.js file from the ghacksuserjs/ghacks-user.js GitHub repository but you need not download it directly. Instead, grab their (Linux) or updater.bat (Windows) script by clicking the file name, then clicking the 'Raw' button in the new page and, finally, Ctrl+S to save the file to your Firefox profile directory. Finally, use the same method to get a copy of their (Linux) or prefsCleaner.bat (Windows) and place it in your Firefox profile directory. This script is used to reset any unused or old preferences in your prefs.js file. If you're running Linux, don't forget to make the files executable. Next, run the updater script to fetch the 'ghacks' user.js and append the contents of your user-overrides.js to it. In Linux run ./ in a terminal and follow the prompts. If you have given the file the executable flag and still get an error, try grabbing a new copy being careful to use the method described earlier.

At this point it is important to go through the entire 'ghacks' user.js file and read all of the comments and review each of the settings to be sure everything is configured the way you want. As stated above, any preferences you want to change in the user.js file should be copied to your user-overrides.js file in the appropriate section where you will then change their values. Note that if you ever add and then comment out or delete a custom preference in your user-overrides.js which is not contained in the 'ghacks' user.js, and you have run Firefox after doing so, that setting will remain in the prefs.js file. The safest way to remove such preferences is to open about:config in Firefox and reset them (right-click the preference, click 'Reset').

Over time it is possible that your user-overrides.js file will contain preferences that are obsolete. The 'ghacks' user.js file contains a list of these preferences in the section titled [SECTION 9999]: DEPRECATED / REMOVED / LEGACY / RENAMED and these preferences should be removed from your user-overrides.js file. One way to do this is to go through the list line by line and see if they are duplicated in your user-overrides.js, but this is time consuming. An easier way is to use the -c switch (documentation here) when you run the updater script which will output a 'diff' file containing the differences between the old user.js and the new one.

IMPORTANT: Don't forget to run the updater script with the -c switch every time you update the user.js file or make changes to the user-overrides.js file. You can read more about the updater script here and the cleaner script here.

Verifying the integrity of user.js

It is important to perform an integrity check whenever the 'ghacks' user.js file is updated or you have changed anything in the user-overrides.js file.

From the 'ghacks' crew:

In FF60+, not all syntax errors cause parsing to abort i.e. reaching the last debug pref no longer necessarily means that all prefs have been applied. Check the console right after startup for any warnings/error messages related to non-applied prefs.

They reference the article, 'A New Preferences Parser for Firefox' if you're interested in knowing more.

To perform this check, you should disable your network connection, then start Firefox and open the Browser Console from the Web Developer toolbox (Ctrl+Shift+J might work) and check for the error messages as advised.

The reason it is suggested to disable your network connection is because, in the event there is a problem with an important preference, a network connection may allow data to flow in or out which you wanted to avoid.

Now we will further check the integrity of the user.js and user-overrides.js files. You may have noticed a bunch of unusual looking _user.js.parrot preferences in both files. These are used for troubleshooting syntax errors by quickly identifying a specific section in which the error lies. When you run Firefox for the first time after updating the user.js or making changes to your user-overrides.js, check the value of the troubleshooting preference by entering about:config in the address bar and searching for the _user.js.parrot preference (it will likely be the first one listed without having to search). The value should match the very last _user.js.parrot preference value in your user-overrides.js or, if you are not using a user-overrides.js, then it should be the last value in the 'ghacks' user.js, "SUCCESS: No no he's not dead, he's, he's restin'!". If the value for the troubleshooting preference is not what you expect, then you can use it to quickly determine in which section of the user.js or user-overrides.js the syntax error lies. While it cannot narrow down the problem to a specific preference or line number, at least you will know where to begin looking.

Updating the user.js file

To update the 'ghacks' user.js file just run the updater script with the -c switch as explained earlier. To update my personal user-overrides.js file, just copy the contents of the new version to your user-overrides.js, then run the updater script with the -c switch. Lastly, run the 'ghacks' prefsCleaner script with Firefox closed. To be notified of updates to the 'ghacks' user.js and/or my user-overrides.js files, i strongly suggest subscribing to the following:

HSTS tracking

To understand how HTTP Strict Transport Security (HSTS) works and how it can be used to track browsing history, as well as the implications of disabling it, read How to prevent HSTS tracking in Firefox on the ghacks website. Setting the preference security.cert_pinning.enforcement_level to '0' may disable HSTS and Public Key Pinning, however there is a security risk in doing so. If you set the preference to '0' and experience the error "The server uses key pinning (HPKP) but no trusted certificate chain could be constructed that matches the pinset.", reset the preference. Likewise if you set the preference to '2' and experience the error "MOZILLA_PKIX_ERROR_KEY_PINNING_FAILURE", reset the preference.

uMatrix usage

!!! SET THE SCOPE, LOCK THE LOCK !!! Keep that in mind as you read this section.

You will likely be spending far more time with uMatrix (uM) than all the other add-ons combined and, being it is one of the most important ones in the pile, it is vital you understand how to use it, so read the wiki because i'm not going to go into great detail here.

When you first install uMatrix, it will allow all 1st party requests by default and we need to sledgehammer that, so load up in a new tab and click the uM toolbar icon to display the main pop-up interface:

Because you have read the uMatrik wiki (you did, right?), you already know that YOU MUST REMEMBER TO SET THE SCOPE in which uM operates before making any changes. Failing to do this will threaten your privacy and/or security. You also know that any changes you make are temporary unless you save them. Since we first want to set some basic default filters that affect all websites, we need to change to the global scope:

Once we're operating in the global scope, i suggest setting up uMatrix to allow CSS, images and, if you're using Site Bleacher, 1st party cookies, all globally. Optionally you may want to allow 1st party media and/or frames globally.

The configuration above will result in the following behavior:

  • 1st party cookies will be allowed globally
  • CSS will be allowed globally, including 3rd party CSS
  • Images will be allowed globally, including 3rd party images
  • 1st party frames will be allowed globally

Unless you only want your changes to be temporary, always remember to click the padlock icon to save them.

Note that in the screenshots that follow, the 1st party cookies block will not always be green as in the one above due to an oversight on my part when i created the screenshots.

Now load up this post in a new tab. Does it look like something's missing? Sure enough, if we open the uMatrix pop-up interface again, we see (or just in the resource list which should tell you that there must be a YouTube video in that post that is being blocked. It also tells you exactly what was blocked, in this case a single frame:

If uMatrix is hiding the subdomains and you don't see, click this little thing in the 'all' row and it will expand the list of domains:

In the screenshots above you can see we are operating in the local scope ( You will notice that i allowed all requests for the 1st party domain,, because it's my site and i trust it. You need not do the same and, as a rule of thumb, you should not do the same, nor is it required to get the video to play, at least not on

So we want to get that YouTube video working, but do we want to allow embedded YouTube videos for only, or for all websites? This is what you need to be thinking any time you want to allow requests for resources. Since you probably want to allow YouTube videos for all the websites you visit, we need to switch to the global scope and unblock the blocked frame for either the domain or the domain. Which you choose depends on whether you want to allow the resource for the root domain, including any sub-domain, or only the sub-domain. In this instance i suggest keeping it simple and allowing the frame for the root domain and all subdomains as shown. Make sure you save the change:

Now when we refresh that page, we might expect to see that YouTube video, but we don't. Opening the uM pop-up again and switching to the global scope, we discover that allowing the frame for caused more stuff to show up, this time a script for as well as another for a new domain,

Making sure your are working in the global scope, let's unblock scripts for and Make sure to save your changes:

Now when you reload the post page, everything should look good. We see the video frame and a nice image. Great. Click the play button and… nothing! Open the uM pop-up once more and we find that we need to allow XHR for the domain. You know what to do, so go ahead and make the change, making sure you're working in the global scope and remembering to save your change afterwards. Refresh the page again and click the play button on the video. It still doesn't work! Again, open the uM pop-up and you'll see another new domain has appeared, this time (in case you didn't know, Google owns YouTube). If is not displayed in the list, hold your Shift button when clicking the reload icon on the uM toolbar. Again, make sure you're working in the global scope and unblock the XHR requests for and save your changes:

Now refresh the page one last time and the video should play. If it does not, you probably messed something up and there's a fair chance it's because you made one or more changes in the wrong scope and tried to correct them. If you messed something up, open the uM Dashboard, click the 'My rules' tab and in the 'Temporary rules' pane, delete all of the rules you created related to YouTube videos and, but be careful not to delete the default rules or the global rules we set up originally. To do this, select the rules and press your delete key, then click the 'Save' and 'Commit' buttons:

Once you've deleted those rules and committed the changes to the 'Permanent rules' list, go back to the first step and try again.

De-borking other websites is generally not as time consuming as it was to get embedded YouTube videos to play and instead is usually accomplished with a couple mouse clicks and a page refresh. Just remember to turn to uMatrix first when a website is busted. If it is blocking something it will let you know by displaying a badge on the toolbar icon. uBlock Origin will do the same, but it won't usually be the cause of the problem since we offloaded its dynamic filtering to uMatrix by not enabling its advanced mode of operation. Again, make sure you read the uMatrix wiki.

Another way to get a website working quickly is to check if there any user created rule recipes available for the site you're visiting or the resource it wants to load. If there are, that little puzzle-piece icon on the uM pop-up interface will become active and from it you can click a rule-set to import. Make sure you set uM to operate in the scope you want before importing the rule-set. Also be aware that user created rule-sets may allow more than you want to allow, however you can always adjust as necessary before saving the changes. User rule-sets can be helpful in determining why a site does not function properly. By the way, you could have done this with instead of letting me drag you through the mud, but that was a good learning exercise.

Lastly i want to stress the importance of both the uBlock Origin logger and the uMatrix logger which are invaluable tools for troubleshooting the tougher problems. You can get a better understanding of the uM logger by reading the documentation for the uBO logger since it is far more complete as of this writing, though some information is uBO specific. The uM logger is available in the Firefox sidebar in addition to a browser tab. This can be really handy because you can set it to display all of the network events it records and watch in real-time as you troubleshoot something without having to swap tabs constantly. Since uBO is configured to run in 'easy' mode, you should use the uM logger when you want to troubleshoot a website.

THE END (lie)

While there are many more things you could do if you're really concerned about protecting your privacy and browser integrity, i hope this guide has been of some use to the technically adept novice or intermediate web surfer at which it is aimed. I welcome any questions or comments you may have, just please leave them in the comment section so others can benefit (you need not be logged in).

Lastly i want to again thank all of the dedicated and skilled people who created, maintain and contribute to the ghacks-user.js repository, especially Thorin-Oakenpants (aka, 'pants') and earthlng. This guide would never have been as comprehensive as it is without the benefit of that bunch of misfits :) Also i'd like to thank the many people who make privacytoolsIO possible. Their website is an excellent resource for those looking to protect their privacy and security.

IMPORTANT: If you incorporate suggestions made in this guide, please subscribe to the Firefox category on the subscription page. This article is updated fairly often and it's the best way to stay informed.


Further reading on this website

The 'ghacks' repository on GitHub

Everything else

Revision history

Click to expand...

custom Scroll to the bottom to see the latest changes.


  • first publishing


  • removed all Shim Storage add-on information since this functionality is duplicated in HTTP UserAgent cleaner.
  • almost all of the documentation for HTTP UserAgent cleaner was heavily revised.
  • various other edits and corrections.


  • updated user.js file
  • several other small updates and a few corrections


  • updated user.js file
  • switched uBlock versions since a new fork was created
  • updated uBlock images and documentation
  • added a "Current notices" section
  • misc. other corrections/updates/edits


  • updated and added more information for uBlock
  • updated one HTTP UserAgent cleaner screen-shot
  • misc. other corrections/updates/edits


  • updated HTTP UserAgent cleaner information
  • for HTTP UserAgent cleaner settings, the suggested settings were split into Suggested global setting for casual browsing and Suggested global setting for best protection.


  • updated information for HTTP UserAgent cleaner
  • updated user.js file
  • minor updates to uBlock information
  • misc. other minor changes


  • updated some HTTP UserAgent cleaner information
  • deleted information for 2 bugs regarding the X-Forward-For setting for HTTP UserAgent cleaner since they were not bugs
  • misc. other minor changes


  • updated information for HTTP UserAgent cleaner, including adding descriptions for the newly added features, Canvas and Fonts on the HTTP tab
  • updated the user.js file
  • updated some definitions of terms used in this document
  • added some more resources


  • updated the information for the Fonts filter on the HTTP tab of HTTP UserAgent cleaner


  • updated HTTP UserAgent cleaner information to match changes in version


  • added Pure URL as a suggested add-on
  • updated contents of the user.js file
  • added and edited some information for HTTP UserAgent cleaner
  • added more resources in the References section


  • updated list of recommended filters for uBlock
  • updated user.js file contents


  • updated user.js file contents
  • updated a few settings recommendations for HTTP UserAgent cleaner


  • minor updates to user.js file contents


  • added information for securing DNS traffic
  • misc. minor updates


  • switched to Raymond Hill's version of uBlock
  • updated uBlock filter information
  • added Fetch information for new version of HTTP UserAgent cleaner
  • updated user.js file contents
  • misc. minor updates


  • updated uBlock settings to match the current development version (
  • misc. minor updates


  • removed HTTP UserAgent cleaner since it is no longer being developed
  • removed Self Destructing Cookies add-on since its functionality can be handled by uMatrix
  • added uMatrix


  • added more info for uMatrix and IP Config test results
  • updated user.js file contents
  • various other edits


  • Minor edits for uMatrix usage text


  • updated user.js file
  • removed pcxFirefox as a suggested 3rd party build since i had display corruption issues with it


  • updated user.js file contents


  • updated user.js file contents


  • updated guide information
  • updated user.js file and added a revision history to the file


  • updated user.js file


  • updated user.js file
  • minor grammar/spelling corrections


  • corrected an error with pref 'layout.css.devPixelsPerPx' where the value was an integer instead of a string – this caused all prefs following it to be ignored


  • set 'browser.fixup.hide_user_pass' back to its default value
  • added 'network.http.redirection-limit'


  • added some basic information for configuring the Clean Links add-on


  • corrected 'plugin.scan.*' values to be strings
  • added bogus preferences in the user.js file at the end of each section for troubleshooting potential loading problems


  • changed the name of the troubleshooting/bogus preference to and added values to indicate the point at which the file stopped loading – a huge thanks to commenter 'Pants' for suggesting the troubleshooting preference and also for suggesting a far better way of implementing it than what i had done (by the way, 'Pants' is the author of the user.js config file used in the 'ghacks' article, A comprehensive list of Firefox privacy and security settings by Martin Brinkmann, so i'm very glad to have his input here)


  • removed duplicate preferences in use.js file (see change-log in the file for details)


  • removed Extension Defender from the list of recommended add-ons since it's home page is gone and the code hasn't been updated in two years
  • updated user.js file


  • switched to using Pants' config v0.11 and mostly just appending my settings to the end of his – because this is a major update, no history of changes to individual preferences will be published


  • published my user.js on GitHub which was forked from Pants' code
  • removed my user.js code from this page and linked to it on the GitHub page instead
  • changed my versioning scheme to match Pants' where the user.js version coincides with the version of Firefox it was developed for, so v51r1 would equate to version 51.x of Firefox and the r1 signifies the revision, in this case the first revision
  • updated user.js to include v51 of Pants' config – no preference changes so far as i know, just added/removed/changed comments
  • updated text in user.js section to account for the new changes
  • changes to comments and troubleshooting preference names and values, other minor changes


  • updated user.js to version 51r2 – see the GitHub page for the change-log
  • updated info here regarding the user custom preferences section of user.js


  • deleted the GitHub repository which i forked from Pants' 'ghacks' repository and created a new repository which does not include his code
  • some changes to user.js
  • some major editing of this document mostly in regard to the creation and changes of the GitHub repositories


  • rewrote and updated much of the content pertaining to uMatrix
  • added section "Removing system add-ons"
  • added section "Sanitizing the default search engine plugins"


  • added some add-ons to the recommended section
  • misc. minor edits


  • i didn't keep track of all the changes and many were made – you'll have to re-read the guide :)


  • added section "A special note about cryptocurrency miners"


  • added more info about IndexDB storage in the "Terminology" and "uMatrix configuration" sections.


  • added to the list of recommended add-ons
  • updated some content to reflect the current state of Firefox and WebExtensions
  • misc. minor edits


  • added a link to my post about the Firefox add-on, Looking Glass
  • misc. minor edits


  • minor edits


  • removed cryptocurrency miner section
  • removed information about the OpenH264 Video Codec plug-in since it seems Firefox is no longer shipping it, at least not on Linux
  • removed the Load from Cache add-on
  • removed some information about uMatrix since uBlock Origin covers most everything uMatrix does and is better suited for removing advertisements, plus it's a much more active project.
  • updated some information
  • note that many more updates will occur in the next days, so i would suggest waiting until they are published before following this guide


  • rewrote most of this guide, so if you read it before, read it again :)


  • added the section 'Firefox profile in RAM'
  • misc. other minor edits


  • lots of clarifications and polishing, added several resources


  • added uMatrix to the add-on pile again
  • added the uMatrix sections of this document
  • removed info about running uBlock in advanced mode since we're using uMatrix for dynamic filtering instead
  • several minor edits
  • polishing


  • add Cookie AutoDelete as a highly recommended add-on and updated configuration information for uMatrix to allow 1st party cookies by default
  • removed information about the Forget Me Not add-on
  • added information about First Party Isolation
  • added rule to uM to prevent web workers
  • added information about the uBO and uM logging functions
  • corrected some mistakes
  • polishing


  • added info about using the user created rule sets for uMatrix, as well correcting some mistakes and clarifying other uM info
  • polishing


  • added info about HSTS tracking
  • minor edits


  • added more info to the uMatrix section, particularly about indexedDB storage
  • minor edits


  • clarified much information regarding the user.js files as well as other parts
  • added more info about browser fingerprinting
  • added more detail regarding system add-ons
  • added a user-overrides.js template
  • updated Header Editor rules download
  • added several more 3rd party resources
  • misc. minor edits


  • added POOP as a required add-on and accompanying configuration information
  • configuration information for Neat URL was located in the wrong section
  • minor polishing


  • minor clarifications


  • add notice about newsletter subscribing
  • corrected advice regarding spoofing the referrer which was suggested for both POOP and uM (now it's enabled in uM only)
  • dumped Cookie AutoDelete add-on – not needed when using uM and First Party Isolation, nor are any of these storage cleaning add-ons able to delete IndexedDB storage due to a shortcoming in the WebExt API, which is another reason to enable FPI
  • removed privacy.firstparty.isolate = false in user-overrides.js in order to enable First Party Isolation
  • added Restrict to Domain add-on to toggle privacy.firstparty.isolate (FPI) via toolbar button
  • removed the list of optional add-ons (NoScript and Smart Referrer)
  • minor edits
  • coming up: looks like i may be recommending to disable FPI in the very near future and use the Temporary Containers add-on instead – i'm playing with it now


  • added some more info regarding HSTS tracking and the SiteSecurityServiceState.txt file based on user feedback – it appears some AV's might have a problem if this file is set to read only
  • added a new resources section specific to the 'ghacks-user.js' GitHub repo
  • added Temporary Containers (TC) add-on and associated info – this results in several major changes throughout the guide
  • added Firefox Multi-Account Containers add-on and associated info – this is used in conjunction with the TC add-on
  • added 'Using containers' section
  • removed Canvas Blocker add-on – not needed with TC
  • removed Restrict to Domain add-on – not needed with TC
  • removed Don't touch my tabs! add-on – (probably) not needed with TC
  • removed Header Editor – not needed for what we were using it for since the function is handled by TC
  • re-added privacy.firstparty.isolate = false to user-overrides.js
  • edited some uMatrix info regarding its privacy settings to reflect changes as a result of the TC add-on
  • added more info about importing rule-sets for uMatrix
  • moved Smart HTTPS add-on to the required section
  • moved Skip Redirect add-on to the required section
  • removed the suggested add-ons section
  • corrected mistakes and updated info in the section regarding integrity checking of the user.js/user-overrides.js files
  • reworked and updated the entire user-overrides.js file
  • removed mention of the template user-overrides.js file and associated download link – user should use the one provided in my GitLab repo
  • several minor edits/clarifications


  • minor edit


  • clarify information regarding the downloading of the configuration files thanks to a commenter
  • updated user-overrides.js
  • fix minor typo


  • minor polishing


  • updated info on HSTS tracking
  • updated info regarding downloading my user-overrides.js file


  • added a link to a comment by 'Bushdoctor' who was kind enough to provide information about loading Firefox profiles in RAM for Windows users


  • added instructions for cleaning user-overrides.js of obsolete preferences
  • minor edits


  • removed info about manually cleaning the user-overrides.js file in favor of using the -c switch when running the updater.js/updater.bat script
  • added Site Bleacher to list of required add-ons
  • removed all info regarding containers as well as the Temporary Containers and Firefox Multi-Account Containers add-ons – i prefer to enable privacy.firstparty.isolate (the default in the 'ghacks' user.js) in combination with Site Bleacher (far less headaches)
  • replaced Neat URL with ClearURLs – while the former is a good extension, i think the latter is even better
  • replaced Smart HTTPS with HTTPZ
  • moved all add-on settings info to the required add-ons section
  • uBlock: added info for globally blocking 3rd party fonts while allowing 1st party fonts
  • misc. edits


  • several clarifications and minor edits


  • minor edits


  • minor edits



  • removed mention of LibreFox (project is currently stalled due to legal nonsense)
  • minor corrections, clarifications and edits


  • moved my Mozilla rant to a separate page
  • added a cryptominer block filter URL to uBlock


  • added a note about enabling the search bar on the navigation bar
  • minor edits


  • added note that this guide is not intended to be use with the Tor browser
  • minor edits


  • very minor edit


  • updated setup instructions for HTTPZ
  • minor edits

234 thoughts on “Firefox Configuration Guide for Privacy Freaks and Performance Buffs”

  1. Thanks for this very great guide. I implemented everything a few weeks ago and so far everything just works. Of course some sites breaks but nothing I haven't been able to fix so far.

    One question though; What is the best solution for Netflix? Should I create another Firefox profile or install another browser for that, and if so, which one?

    Thanks in advance.

    1. hi Simon – thanks for the positive feedback

      i don't use Netflix, but what i would do is fire up a fresh Firefox profile, drop the ghacks config in it, then start troubleshooting to see what pref(s) is causing the site to break, assuming it's the ghacks config

      no need to use another browser unless the site simply won't work with default Firefox – also, everything that a website can store client side is contained in your profile directory, so if you create a new profile, it is completely isolated from your old one

      if you find you have to use another browser, i have no recommendation – maybe Opera or Chromium (not Google Chrome)

  2. Thank you very much for the guide.
    I do have a one problem: How to block whhich links started with Firefox and addons. I did use my firewall to block them but then it stopped some addons (I have just what you recommended).
    Do you think reset Firefox will hel?
    Thank you.

    1. i think if i were you i would uninstall Firefox and rename your profile folder (add .bak to it or whatever), then reinstall Firefox and transfer anything you need from the old profile (bookmarks and such) to the new one – then of course you'll have to go through the guide again

        1. that appears to be related to search – if you look further in about:support, you'll also see google, bing, etc.

          i have this "extension" also on Manjaro (Arch) – i hate that Mozilla does this crap, but there are no privacy concerns with the default search engines that i am aware of as long as you don't use them

  3. Hi, great guide, thank you for that.
    I noticed that uBlock Element Picker stopped working when I set up uBlock and uMatrix like you lined out. Any way to get it back working?

    1. the only way to enable the e-picker (that i know of) is to enable advanced mode in uBO, which is fine, but if you want to use uM then just remember not to use the uBO filter settings

      what i do is install Stylus and i use that for hiding stuff – it does a fantastic job, but you have to know a little about CSS

      1. Hm, I tried with enabling advanced Mode, but it does not seem to work. What exactly do you mean with not using the uBO filter settings? The hosts files in uM (I configured both extensions exactly how you described)?

        Thanks, I will take a look into that Stylus extension.

        1. you're right – enabling advanced mode doesn't enable the element picker by itself – i figured out how to make it work from the uBO wiki

          apparently you don't have to enable advanced mode at all – instead, make sure "Disable cosmetic filtering" is disabled in settings, then on the "filter lists" tab, enable "Parse and enforce cosmetic filters" – if that alone doesn't work for you, reload uBO (disable it from about:addons, then enable it again)

          just as an FYI, element picker achieves the same result as Stylus i think in that it does not block anything from being loaded by the browser like the uBO filter lists do, rather it simply hides it – personally i prefer Stylus for this since you can not only hide elements, you can also change the appearance of them, such as colors, font sizes, dimensions, etc. – anything you can do with CSS – the down side is you have to be a little familiar with CSS, but creating CSS rules is pretty easy using the FF developer toolbox, inspector tool (Ctrl+Shift+C) which also has an element picker to help create rules

          1. Thank you so much, worked like a charm.
            Setting it up like this does not hurt privacy more, does it?

            Also: Is Privacy Possum unnecessary when using the uB+uM combo?
            And since uM apparently does not have the user agent spoofing anymore, I installed User-Agent Switcher (managed to get my browser to show a Tor Signature on with the help of your addon combination + the UA Switcher.)

              1. I see, very helpful link, thanks.
                Site Bleacher takes care of cookies, so no Cookie Autodelete needed, right?

                Why do you recommend httpz over https everywhere btw.?

                1. yes, Site Bleacher handles so-called cookies and a couple other types of storage, including IndexedDB, so no, CAD is not needed

                  HTTPS Everywhere relies on static lists and apparently there is a human component in creating these lists, thus it will never be 100% accurate, plus it uses quite a bit of memory relative to its function – in my opinion this is a cave man approach, whereas HTTPZ doesn't give a crap what kind of connection a site supports, it always attempts an HTTPS connection and, if that fails, only then will it degrade to HTTP (and you can config it to warn you beforehand)

                  there is a bit more to the story and both have advantages, but i prefer HTTPZ because you install it and forget about it and it just works, minus some more complex situations that don't crop up a whole lot

                  1. Interesting, didn't know that.

                    Do you also have problems with recaptcha lately? I enabled it in uMatrix and can klick on the box, but nothing happens except after the secont time I get a "Could not connect to the reCAPTCHA service.

                    Please check your internet connection and reload to get a reCAPTCHA challenge."

                    Any ideas what could cause this?

                    1. there's a bunch of things that can interfere with google recaptcha and i'm not sure there's a complete working solution other than to spin up a new profile and use it for the captcha bullshit – and it IS bullshit – google is using this incredibly annoying nonsense to collect data and i suspect there's a lot of very personal and unique data that can be collected with it according to how and how long one takes to solve it, etc. – i think might be kind of like identifying one by their writing style (and yes, that's a thing)

                      apparently using a VPN can cause issues where the captcha will take longer to solve – other preferences will simply break captcha, as you experienced or, again, add significantly to the number of questions asked before it is solved

                      with the ghacks user.js and my user-overrides.js, and with the extensions i use and the way they are configured, it seems i can solve them some or much of the time, but i'm not sure they are solvable all the time, and they take a very long time to solve

                      there was a lengthy discussion on the subject on ghacks somewhere…

  4. Trying again; might have bounced. Please forgive the temp email, but I don't know if you use auto-encryption (proton or tuta maybe). Thank you for any help here or on like-post at r/privacy.

    I don't see the following four settings in HTTPZ and POOP:

    HTTPZ settings
    Global mode: aggressive Setting not found
    Other: Spoof cross origin Referer: disabled (this is better handled by uMatrix from a convenience standpoint)
    Setting not found

    Privacy-Oriented Origin Policy (POOP)
    "Settings: I would recommend setting the 'Global mode' to 'aggressive' and enabling the 'Exclude root domain matches' option. If you not are using uMatrix, enable the 'Spoof cross-origin Referer' option."
    These two settings not found

    I don't see a "Global Mode" in FF either. How do I set these?
    uBO settings
    ! allow 1st party fonts globally (*$font,third-party), 3rd party by domain (,|
    ,| # In My Filters, do I add this third line?

    "If you're using the Decentraleyes add-on you should add some rules to the 'My Rules' tab in the Dashboard. I recommend doing this even when uBO is configured for 'easy' mode, as the case here. When adding the rules, be sure to remove any conflicting rules for the same domains if you have any (you won't if you're starting fresh)."
    # It looks like I accumulated many rules from prior uBO use. Should they be cleared to start again in uMatrix?
    In overrides:

    * [SET] these are preferences i'm testing or which will probably appear in the
    * 'ghacks' user.js in the future – you may want to copy the active ones to
    * the USER CUSTOM PREFERENCES section and comment them out, then run the
    * 'ghacks' updater and prefs cleaner scripts

    Comment them out below, in user custom prefs, or the other way around? If it is the former, how will the ghacks updater act on my prefs?

    * ——————————————————
    * exit Firefox and comment out the preference(s) by prefixing it with 2 forward
    * slashes (//), then run the 'ghacks' updater script followed by the 'ghacks'
    * prefs cleaner script

    The user could exit ff to make one or two changes as instructed; however, could they also make numerous changes, and run updater just one time? Also, can ff remain running during editing, as long as it is closed when the ghacks scripts are run?

    Please forgive the length, and Thank You!

    1. HTTPZ: ignore those settings – he updated the add-on – the defaults are fine, but you can disable automatic mode

      POOP: the 'global mode' settings are in POOP, not Firefox – those settings are there – look again

      uBO, font filter: that's actually 2 lines, not 3, and and both get pasted in 'my filters' – the first line is a comment that explains how to edit the filter…

      ! allow 1st party fonts globally (*$font,third-party), 3rd party by domain (,|

      Decentraleyes: …

      It looks like I accumulated many rules from prior uBO use. Should they be cleared to start again in uMatrix?

      be careful what you clear – you don't have to clear anything, just make sure the Decentraleyes rules don't conflict with existing rules

      The user could exit ff to make one or two changes as instructed; however, could they also make numerous changes, and run updater just one time?


      Also, can ff remain running during editing, as long as it is closed when the ghacks scripts are run?

      yes – you can even run the updater script while FF is running, but the settings won't take effect until it's restarted – the cleaner script must be run after exiting FF else… else i don't know what will happen :)

      thanks for mentioning this stuff – i see i need to make some corrections in the guide

      also, it sounds like you're a little shaky with this stuff, so go ahead and read the Decentraleyes and uBlock wiki's – links are in the guide

      1. Searching "POOP" led to the wrong extension. Typing out "Privacy-Oriented Origin Policy" led to the right one, of course.

        I studied the settings, made some edits in my copy of overrides, and ran the update files as instructed. The parrot user pref did not trigger until the last value, " USER SETTINGS LOADED", but the other integrity check is not clear to me. The instruction says to "check for the error messages as advised" in the browser console. There are all kinds of errors, warnings and more. I'm poking around and researching a little, but how much is relevant to the "user js" files, and will said advise be in those messages? Ghacks "1.4 Troubleshooting" instructs the console a little bit, but that is for interacting later with an internet connection.

        1. The parrot user pref did not trigger until the last value, " USER SETTINGS LOADED"

          that's expected as i think you already know – that value indicates there's no syntax error in the any of your configs

          re: the console errors, i can't give you any proper help because i'm frankly not overly familiar with how to determine what error is attributed to what – given what's stated in the ghacks wiki any error due to the prefs files should be obvious however

          i also have several errors when FF starts with no sites/tabs loaded and i'm fairly sure none of them are due to preferences

          whether the errors you're experiencing are due to the prefs files is easy enough to test – just rename user.js and prefs.js and see if you see the same errors – i need to test this myself too and i'll post back as soon as i do (won't be today) – in my case i know a couple of the errors are due to extensions

          do some testing on your end and let me know what you find and i'll do the same here

          if you want, send me a reminder from the contact form to make sure i don't forget about this

        2. i just did a test where i edited a preference in user.js so that it would create an error in the browser console, which it did – the error happened to be the very first in the list and included the string prefs parse error:

          /home/[user]/.mozilla/firefox/ju8ef1bs.default/user.js:2095: prefs parse error: unknown keyword

          it's a rather vague error, but at least it informs one that it's a preference issue

  5. Regarding "Firefox profile in RAM" and "Windows":
    For me it works fine with a Windows compatible software for managing RAM disks called "ImDisk Toolkit" and scripts for handling of the Firefox-profile(s).

    "ImDisk Toolkit"
    Scripts for handling the Firefox-Profiles (be sure to read the whole page – there are some corrections of the scripts):

  6. I thought
    "If you want the -merge function to comment out a pref you have to use this exact format:
    //// — comment-out — '' "
    // 2668: extensions.enabledScopes "
    was something to this effect, but I wasn't sure how to use it.
    But if it is not possible, I will do it manually.

    1. i didn't even know -merge existed (i don't use windows) but from what i see it appears you can only comment out single prefs, not blocks – you can ask on their github repo though

      just a reminder in case you don't already know – if you comment out a pref after having run FF, it will still exist in prefs.js, so if you want to change the value, reset it from about:config

  7. Great work, thank you!
    There is one thing I haven't understood using the user-overrides.js file. Is there a way to comment out or delete parts of the user.js file, with the help of the user-overrides.js? I read the wiki, but it is not clear to me how to do it.

    1. unfortunately not – the only option one has is to copy prefs from user.js to user-overrides.js and change their values

      on a side note, if you followed my guide and noticed any issues, let me know – thanks

  8. I have a quick question about the setup for the Poop extension. Why do you recommend to enable the setting 'Spoof cross-origin Referers' when all Referers are already handled by uMatrix? It might cause some breakage when two extension try to do the same thing, but please correct me I'm wrong.

  9. a note to everyone who has subscribed to comment notifications for the article 'Firefox Configuration Guide for Privacy Freaks and Performance Buffs' – there have been and will continue to be important changes made to this guide and i would highly suggest subscribing to an email newsletter specifically for this article so you can be notified of the coming changes – you can subscribe here

  10. I have the following add ons : canvas defender-canvas blocker-blockchain DNS-cookie autodelete-css exfil protection-decentraleyes-Disconnect for facebook-Dont touch my tabs-facebook container-google search link fix-Header editor-HTTPS Everywhere-link cleaner-No Coin-NoScript-Privacy Badger-Privacy Enchanced Mode for Embedded Youtube-Privacy Possum-Privacy Settings which one does not need

    1. you will need to sort out what add-ons you need by doing some research yourself – the list of add-ons you use is very different than those i suggest in the guide

      that said, you're running 2 canvas add-ons which is probably not a good idea and Blockchain DNS appears to work only for a few crypto coin TLDs and not any common TLDs like .com, .net, .org, etc., so it's only useful if you use those TLDs

      what Privacy Enhanced Mode for Embedded YouTube does you can do with Header Editor

      if you used uBlock Origin and/or uMatrix, you could eliminate many of your add-ons and be generally better protected

      1. I forgot to write to you that I have and uBlockOrigin-uMatrix (with all the settings you suggest)

        skip redirect-Smart HTTPS – TrackMeNot- User Agent Switcher- WebRTC control- Privacy Oriented Origin Policy- Project insight

        and because I am afraid I have extensions that do the same job i would like your opinion on what to hold and what to remove

          • TrackMeNot – not needed – covered by uM, uBO list subscriptions, ghacks user.js
          • User Agent Switcher – dump it – you can enable UA switching in uMatrix if you want to do so
          • WebRTC control – dump it – enable the WebRTC option in uMatrix
          • Privacy Oriented Origin Policy – set this to 'relaxed' in the options if you're new to this, else a lot of websites will break
          1. I deleted it TrackMeNot,I followed your instructions about uM,I hope to be covered and do not need any other regulation

            I deleted it and User Agent Switcher also I followed your instructions about uMatrix and I hope to be covered and do not need any other regulation

            I hope your arrangements are included the webRTC control via uMatrix,

            Privacy Oriented Origin Policy – i set this aggresive and and in some sites which fell as youtube I changed the setting to use global setting,also ran out of the settings and turned on exclude root domain matches

            HTTPS EVERYWHERE and SMART HTTPS do same job?

            1. yes, HTTPS Everywhere and Smart HTTPS do the same job

              if you don't use WebRTC (chat, camera, microphone) you can set media.peerconnection.enabled to false in your user.js if you are not using the ghacks user.js (is set to false in the ghacks version)

              for POOP you can add these rules in the Exclusions section:

              * *

              and then delete any of the corresponding rules in the Overrides section that you added to get videos to work

  11. As interesting and revealing as the topic appears, the discussion would make much sense if one was knowledgeable on the subject. I am an internet enthusiast that is very concerned about privacy. I would appreciate suggestions -free :) :)online resources and other free stuffs-that would help me understand the basics and trust me I would go all the way up from there to become a valuable contributor like "Pants","Stoically","Alex Leyton" and the rest of you. Shall we get started on making a layman into a guru

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