Firefox Tweaker

What is Firefox Tweaker?

Firefox Tweaker is a tool that allows users to easily control aka “tweak” hidden Firefox 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 silly 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.


Firefox Tweaker download


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”

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