Firefox Tweaker

What is Firefox Tweaker?

Firefox Tweaker is a tool that allows users to easily control aka “tweak” hidden Firefox web browser settings. These tweaks are mostly a result of silly design decisions by Mozilla and they go out of their way to make them super difficult to revert or change. Especially now that they have dumbed down about:config tweaks page even further…

How Firefox Tweaker applies tweaks?

This tweaker directly modifies settings within prefs.js file. Because Mozilla’s dumb idea is to kill user.js tweaks soon to save 0.000002 milliseconds of browser startup time, so I’m not even going to bother doing it through user.js and instead modify prefs.js directly. As a safety measure, backup of prefs.js is created on initial run of Firefox Tweaker. You will be notified about it on run-time.

Special thanks

I’d like to specially thank Mozilla designers/developers to bless us with moronic design decisions which forced me to develop this tool in order to easily revert or change them. I wouldn’t have to do it without you!


Firefox Tweaker only works with Windows (and thus only supports Firefox for Windows).

Questions, problems or bugs?

For any questions, problems or bug reports contact me via e-mail or through comment section below.




3.3 (2021-12-18)

  • Added “WebRender SVG”
  • Added “Cascade Layers”
  • Added “AHardwareBuffer”
  • Added “Window Occlusion Tracking”
  • Added “Show “Not secure” text on HTTP”
  • “Suspend Background Tabs” included in “OneClick Configuration”
  • Show “Not secure” text feature included in “OneClick Configuration”
  • Window Occlusion Tracking included in “OneClick Configuration”
  • WebAssemblyGC included in “OneClick Configuration”
  • WebAssembly Caching included in “OneClick Configuration”
  • Removed “Enable Shaders Pre-Caching” because it caused long delay on Firefox startup
  • Removed “Force Sub-pixel AA”
  • Removed “Enable Fission” (enabled by default in Firefox 95)
  • Fixed wrong state of “Enable WebRender SVG” for “Restore Defaults” from TRUE to FALSE

3.2.7 (2021-08-16)

  • Added “Cache Firefox Home” (Performance Tweaks) which speeds up browser startup time when Firefox Home is used as startup page.
  • Added “Opera Style Tab Manager” (Interface Tweaks) which adds an Opera style dropdown menu which lists all currently open tabs, located on the far right side of tab bar. Useful for searching across tabs as well as listing far more tabs than you can physically see at any moment on the tab bar itself.
  • Removed “Disable Toolbar Other Bookmarks” (Interface Tweaks) option because it’s now part of Firefox official settings (has been for a while, but I left it there anyway).
  • Re-arranged “Performance Tweaks” list

3.2.6 (2021-08-10)

  • Removed “Disable Proton Interface” under “Interface Tweaks” as it was disabled in Firefox 91+. With Firefox 91 and newer, Proton Interface is the new interface default.

3.2.5 (2021-08-09)

  • Added “Suspend Background Tabs” feature
  • Renamed “Disable URL bar oversizing” to “Reduce Interface Animations”
  • Added “HTTPS First Mode” under Security Tweaks which always tries to establish HTTPS connection and falls back to HTTP if it fails (Firefox 91+).
  • Removed “HTTPS Only Mode” tweak because it’s now available within Firefox settings

3.2.2 (2021-06-03)

  • Corrected HTTP/3, Web Assembly SIMD and TLS Delegated Credentials settings. These are now enabled by default since Firefox 89+.
  • HTTP/3 tweak functionality has now been reversed and acts as a compatibility option that can be disabled if user desires so. I’ve noticed some webpages like Youtube seem to have problems with Firefox and HTTP/3 (videos take forever to load).
  • Adjusted Restore Defaults and One Click Configuration according to new defaults.

3.2.1 (2021-06-01)

  • Added “Allow Compact Density” tweak under “Interface tweaks”. Mozilla removed “Compact” interface density mode with Firefox 89, leaving only Normal and Touch. With this tweak, Compact will appear again. Firefox Tweaker will also automatically switch to Compact mode when this tweak is selected and revert to Normal when deselected.
  • Added “Allow Compact Density” to “Restore Defaults” feature. Restoring defaults will disable Compact mode and automatically switch interface back to Normal density mode.

3.2 (2021-05-31)

  • Proton Interface is now default Firefox interface (Firefox 89+). Tweak for Proton interface has been adjusted accordingly.
  • Restore Defaults has been adjusted for Proton Interface new defaults in Firefox 89+)
  • HTTP3 and three TLS security features added to One Click Configuration

3.1 (2021-05-15)

  • Added new “Security Tweaks”, all TLS related, preventing downgrading of TLS connections, and adding support for TLS Delegated Credentials and TLS Post-Handshake Authentication.
  • Added new “JavaScript Engine Tweaks” section with two new tweaks for WebAssembly SIMD and WebAssembly GC. Both experimental features to accelerate WebAssembly/JS interaction.
  • Added new “Disable PDF.JS” tweak under “Browser Components” section.
  • Fixed missing entries under “Restore Defaults” for certain tweaks

3.0 (2021-04-26)

  • Redesigned applying of tweaks. You can now disable warning after applying tweaks in “Firefox Tweaker Settings” as well. There are some limitations to that which you can read under its Help button. Only recommended for advanced users who understand how tweaks are applied and will do the process correctly.
  • Added Project Fission, located under “Security Tweaks” section. Firefox 88 seems to already accept the setting. It’s still work in progress by Mozilla.
  • Relocated “Proton Interface” from main tweaks list to “Interface Tweaks” where it belongs

2.9.1 (2021-04-23)

  • Added “browser.proton.tabs.enabled” parameter for the Proton interface tweak. It’s needed to enable Proton floating tabs. Just re-apply the tweak if you’ve used Firefox Tweaker 2.9 before and it will also apply this missing parameter.
  • Slightly re-arranged Proton Interface help text and added additional footnote.

2.9 (2021-04-22)

  • Added “Proton Interface” control for new Proton interface preview. Only available for Firefox 88+. It’s optional for now, but from what I heard Mozilla is planning to roll it full scale to users in Firefox 89. It’s unknown if parameters will be available to users then.
  • Changed my webpage address in About page and program itself from old to new

2.8.2 (2021-01-26)

  • Added “Disable Other Bookmarks” tweak under “Interface Tweaks” which allows you to disable Other Bookmarks button in main bookmarks toolbar which is enabled by default in Firefox 85.
  • Added “Disable Other Bookmarks” into OneClick Configuration as preferred setting (disabling Other Bookmarks button).

2.8 (2020-11-20)

  • Added “Disable Developer Tools” option under “Browser Components” category. This allows users who never need the developer tools to simply get rid of them entirely. Disabling Developer Tools will disable F12 key shortcut for developer tools. It will also remove Menu Bar options as well as right click context menu developer tools access. Most users never need any of this stuff, yet it’s there for everyone. Disabling it makes browsing experience far less cluttered.

2.7.5 (2020-08-30)

  • Added “One Click Configuration” that will apply a curated selection of tweaks in one click.
  • Added “Restore Default Settings” option that can revert ALL Firefox Tweaker tweaks back to default settings in one click.

2.7.1 (2020-08-16)

  • Added option to Disable URL trimming (Interface Tweaks). URL trimming hides away “unimportant” parts of URL address to make it look easier to understand, but will hide URL specifics that might be useful to some. Disabling URL trimming should force Firefox to display full URL addresses at all times.

2.7 (2020-08-02)

  • Further enhanced disabling of WebRTC by enforcing (re-apply the tweak to enforce it)
  • Added new Disk Cache Capacity tweak for adjusting the disk caching between Automatic, Disabled, 1GB, 2GB, 3GB and 4GB capacities.
  • Added WebGPU tweak (Rendering Engine Tweaks)
  • Added Shaders Pre-Caching tweak (Rendering Engine Tweaks)
  • Added Force Sub-pixel AA tweak (Rendering Engine Tweaks)
  • Added Tiles tweak (Rendering Engine Tweaks)
  • Added warning for HTTP/3 as it is causing stalling/hanging of some webpages
  • Some updates of Help sections
  • Minor cleanup of code

2.6.1 (2020-07-26)

  • Added “Close tabs by double clicking” (Interface Tweaks). You can close focused tab by double clicking it. Might be more convenient than chasing a tiny close button on each tab.
  • Renamed few tweaks a bit so their names are not cut in the interface

2.6 (2020-07-13)

  • Added new “Rendering Engine Tweaks” category
  • Moved all the WebRender and rendering related features to new “Rendering Engine Tweaks” category
  • Added “Enable TCP FastOpen” tweak (Performance Tweaks) which should speed up successive TCP connection handshakes.
  • Added “Tracking Protection Performance Mode” (Performance Tweaks) which will apply lower network priority on content coming from tracking channels, giving higher priority to content you want to see and use.
  • Few minor fixes in Help descriptions

2.5 (2020-07-12)

  • Added new “Security Tweaks” category
  • Moved “Upgrade HTTP content on HTTPS pages” to new Security Tweaks category
  • Added “HTTPS Only Mode” (Security Tweaks) which strictly enforces use of HTTPS and blocks HTTP only webpages (Firefox 78+).
  • Few minor fixes in Help descriptions

2.4.4 (2020-07-09)

  • Fixed “Disable URL bar dropdown menu on focus” setting which now apparently uses “browser.urlbar.suggest.topsites” parameter instead of old “browser.urlbar.openViewOnFocus”. This change apparently happened with Firefox 78. While there is a setting in Firefox settings for this, I’m going to leave it in Firefox Tweaker for convenience reasons.

2.4.3 (2020-07-06)

  • Added “Enable HTTP/3” (Performance Tweaks). HTTP/3 uses QUIC mechanism to speed up connection negotiation and connecting to servers. Unsure when Firefox added support exactly, but it’s there for sure in Firefox 78 and newer.

2.4.2 (2020-06-30)

  • Upated “Disable new oversized URL bar” which now uses “ui.prefersReducedMotion” parameter to turn the damn thing off. Only works with Firefox 78 and hopefully in future versions too…

2.4 (2020-06-05)

  • Redesigned “Disable new oversized URL bar” which now uses userChrome.css style sheet in order to disable the god awful oversized dumbass new URL bar. Thank you for providing one.
  • Added mechanism to backup existing userChrome.css . It will still overwrite it entirely anyway when doing tweaks, but it’s there so you won’t lose all your own tweaks. Sorry, but this is the most I can do. Say thanks to Mozilla which forced me to do this god damn hack to disable their new URL bar.

2.3 (2020-06-01)

  • Added “Force Enable Direct2D” (Performance Tweaks)
  • Added “Force Enable HW Video Decoding” (Performance Tweaks)
  • Changed description in Help for “Disable new oversized URL bar” because dumb Mozilla decided to remove this tweak and shove this stupid new URL bar down everyone’s throats even though no one fucking likes it or ever asked for it. Disabling this oversized flashing ugly URL bar introduced with Firefox 75 is now only possible in Firefox 75 and 76. With Firefox 77 you have to use it whether you like it or not. You probably don’t. Enabling this with Firefox 77 will do nothing.

2.2 (2020-05-21)

  • Totally redesigned the prefs.js auto detection mechanism and added GUI driven manual selection or override for situations where prefs.js cannot be detected in default location or when multiple profiles are detected.
  • Added name of the exact parameter used for any given tweak under HELP button. Helpful so you know what exactly is being modified and if I’m interpreting some tweak wrong.
  • Added “Enable HTTPS green padlock” (Interface Tweaks)
  • Added “Disable Beacon API” (Privacy Tweaks)
  • Added “Browser Components” category
  • Added “Disable Firefox Accounts” (Browser Components)
  • Added “Disable Pocket” (Browser Components)
  • Added “Disable Screenshots Tool” (Browser Components)

2.1 (2020-05-09)

  • Added “Performance Tweaks” section
  • Added Enable WebRender setting
  • Added Force Enable WebRender setting
  • Added Force Enable Accelerated Layers setting
  • Added Enable GPU Process setting

2.0.1 (2020-04-29)

  • Added manual profile path override if default mechanism fails to find prefs.js file because your user profile is in non default location or you’re using portable Firefox. It can be done by placing PREFSJS.txt file next to Firefox Tweaker EXE and providing full path including filename and extension to desired prefs.js file inside this text file. There is now also actual file check in place which verifies if path provided is valid and points to actual physical file. If not, you will get an error letting you know you’ve set something wrong.

2.0 (2020-04-12)

  • New interface with modular design ready for the future
  • New custom designed Firefox Tweaker icon (Fox hugging a cog/gear)
  • Toned down the Mozilla hating wording
  • Descriptions of all tweaks are now inside the tweaker under Help button on every tweaks settings page
  • Added special setting to disable startup warning
  • Added quick shortcut to open Firefox Profile folder
  • Added function to clear “Your browser is being managed by your organization.” message
  • Added option to enable Container Tabs without having to install any extension
  • Added option to enable First Party Isolation
  • Added option to disable WebRTC functionality
  • Added option to allow 3rd party cookies for current session only
  • Added option for Firefox to automatically upgrade HTTP content on HTTPS pages to HTTPS as well if possible
  • Added option to disable Default Browser Agent telemetry function

1.0.1 (2020-04-10)

  • Forgot to enable Firefox detection mechanism and turn off some production debugging dialogs (you have only seen them if you had no Firefox installed when running Firefox Tweaker v1.0)

1.0 Initial release (2020-04-10)

  • Added “Disable browser closing on last tab close” (of all browsers only Opera isn’t doing this idiocy by default)
  • Added “Disable new oversized URL bar” (introduced with Firefox 75)
  • Added “Disable URL bar dropdwon menu on focus” (introduced with Firefox 75)
  • Added “Disable Add-ons recommendation”
  • Added “Disable Recent Highlights”

9 thoughts on “Firefox Tweaker

    1. I’m using this framework because it allows me to quickly make whatever I want. It’s really not that inconvenient to use. If you’re too bothered by going through every category, just use “One Click Configuration” option. It’ll set all the important or meaningful options automatically and leaving out more fiddly ones. It’s pretty straight forward otherwise. Main menu holds categories and when you open each, you get individual settings. And that’s about it. Reason you have to start it every time after one of categories is applied is because of how Firefox stores settings and how they are applied directly to the Firefox preferences file. I could do it without restarting, but then it wouldn’t display correct selected checkboxes until settings would actually be applied (as my tweaker appends them at the end of the preferences file and Firefox then automatically reorders them in its own order). It’s still light years faster than manually copy and pasting the settings into about:config and manually flipping them.




  2. Considering it’s been three months and three FF versions, just wondering, what are your Considerations for a next version of the Tweaker app? Kindly advise. Thanks!


    1. I generally don’t have anything in particular to include, but if you are aware of any tweaks in Firefox 93 and 94 that might be interesting, especially if it’s in any way performance related especially, let me know on my e-mail or just here in comments and I’ll check it out and possibly include.


    2. I’ve been using this app for almost a year now. Rarely open it. But when I opened the app yesterday, it asked to select a PREFS.JS file, because with the latest update apparently there are multiple versions of such file now. I couldn’t locate it via Windows Explorer. Kindly please assist. Or should you make an update for the app now?


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