Settings and librewolf.overrides.cfg

While you can always tweak your settings in the Settings page as well as in the about:config page, Librewolf can also be personalized by using a configuration file called librewolf.overrides.cfg.

Using overrides is a great way to change your default settings across multiple profiles and installations, which means that it also allows you to easily backup and port your preferences.

On this page you can find some quick recipes for commonly-requested changes that you can simply paste in your own librewolf.overrides.cfg file, as well as tips for a more advanced setup!

Overrides How To

Where do I find my librewolf.overrides.cfg?

If this is your first time working with overrides, you'll have to create the file yourself. In some cases, you may also have to create the .librewolf folder. The location depends on your operating system and installation method.

On Linux with Flatpak:

$HOME/.var/app/io.gitlab.librewolf-community/.librewolf/librewolf.overrides.cfg

On macOS and most Linux distros (without Flatpak), in the home directory:

$HOME/.librewolf/librewolf.overrides.cfg

On Windows, in your profile directory:

%USERPROFILE%\.librewolf\librewolf.overrides.cfg

Common .cfg Recipes

Simply add these lines to your librewolf.overrides.cfg file. The order is not important, though if you accidentally include the same option more than once, only the last one will be applied.

Enable Google Safe Browsing

If you want to re-enable Google Safe Browsing insert the following prefs in your overrides:

defaultPref("browser.safebrowsing.malware.enabled", true);
defaultPref("browser.safebrowsing.phishing.enabled", true);
defaultPref("browser.safebrowsing.blockedURIs.enabled", true);
defaultPref(
  "browser.safebrowsing.provider.google4.gethashURL",
  "https://safebrowsing.googleapis.com/v4/fullHashes:find?$ct=application/x-protobuf&key=%GOOGLE_SAFEBROWSING_API_KEY%&$httpMethod=POST"
);
defaultPref(
  "browser.safebrowsing.provider.google4.updateURL",
  "https://safebrowsing.googleapis.com/v4/threatListUpdates:fetch?$ct=application/x-protobuf&key=%GOOGLE_SAFEBROWSING_API_KEY%&$httpMethod=POST"
);
defaultPref(
  "browser.safebrowsing.provider.google.gethashURL",
  "https://safebrowsing.google.com/safebrowsing/gethash?client=SAFEBROWSING_ID&appver=%MAJOR_VERSION%&pver=2.2"
);
defaultPref(
  "browser.safebrowsing.provider.google.updateURL",
  "https://safebrowsing.google.com/safebrowsing/downloads?client=SAFEBROWSING_ID&appver=%MAJOR_VERSION%&pver=2.2&key=%GOOGLE_SAFEBROWSING_API_KEY%"
);

If you also want Safe Browsing to locally check your downloads add:

defaultPref("browser.safebrowsing.downloads.enabled", true);

With these preferences set, all the checks made by Safe Browsing will be performed locally, as if you enabled Safe Browsing in about:preferences#librewolf.

Enable letterboxing

Letterboxing helps limit fingerprinting by only expanding or shrinking the inner window size in fixed increments, letting you blend in with a larger number of users.

defaultPref("privacy.resistFingerprinting.letterboxing", true);

Limit cross-origin referers

This override allows you to control when a cross-origin refer will be sent, allowing it exclusively when the host matches.

defaultPref("network.http.referer.XOriginPolicy", 2);

This change might cause breakage: in that case you can revert to the default value and rely on the built-in referer trimming, or alternatively you can use Smart Referer.

Enable WebGL

defaultPref("webgl.disabled", false);

If you enable WebGL, please consider using an extension like CanvasBlocker to retain at least a minimum amount of fingerprinting protection.

Disable media.peerconnection.ice.no_host

This setting was originally intended to protect your private IP address, but it became redundant and can be safely disabled unless you're on Windows 7 or 8. You may need to disable it to get some video conferencing websites to work.

defaultPref("media.peerconnection.ice.no_host", false);

Enable Firefox Sync

For a more in-depth look into Firefox Sync, check the FAQ.

defaultPref("identity.fxaccounts.enabled", true);

Preserve browsing and download history

By default, LibreWolf deletes your browsing and download history on shutdown.

defaultPref("privacy.clearOnShutdown.history", false);
defaultPref("privacy.clearOnShutdown.downloads", false);

Due to a quirk in how these preferences function, if you clear your browsing history, downloads will also be cleared. The opposite, however, is not true: you can clear your downloads without clearing history.

Stop LibreWolf from resuming after a crash

This feature allows you to keep your tabs after an unexpected close event. You can disable it by adding:

defaultPref("browser.sessionstore.resume_from_crash", false);

Enable Autoscroll safely

Autoscroll lets you quickly move through a page by clicking the middle mouse button: a small circle with two arrows will appear on screen, and simply moving your mouse cursor will scroll the page in the same direction. The further way the cursor is from the circle, the faster the scroll.

If you want to enable autoscroll, it's best to disable pasting by clicking the middle mouse button, as otherwise it'd be easy to accidentally paste data into the web page while trying to activate autoscroll.

defaultPref("middlemouse.paste", false);
defaultPref("general.autoScroll", true);

Disable RFP (Resist Fingerprinting)

Careful: RFP goes a long way towards protecting your privacy and we strongly recommend keeping it. Make sure you've read what it does before going ahead.

defaultPref("privacy.resistFingerprinting", false);

Disable OCSP hard-fail mode

If you are experiencing OCSP issues this will change mode to soft-fail.

defaultPref("security.OCSP.require", false);

Enable the extension firewall

The extension firewall denies internet access to your extensions.

Careful: this may lead to extensions relying on outdated data, or flat-out not working, depending on how much they rely on internet access to function. For example, uBlock will not be able to update its filter lists.

defaultPref(
  "extensions.webextensions.base-content-security-policy",
  "default-src 'none'; script-src 'none'; object-src 'none';"
);
defaultPref(
  "extensions.webextensions.base-content-security-policy.v3",
  "default-src 'none'; script-src 'none'; object-src 'none';"
);

Advanced Concepts

The .cfg file is actually parsed like a Javascript file, so the usual Javascript syntax applies if you happen to be familiar with it. The file is read by Firefox on every startup.

There are different functions you can use to set your preferences. You can read more about them on Mozilla's support page

In particular, the main ones are defaultPref() and pref(). The difference, as the name suggests, is that the former sets a default but doesn't override the user's preferences, while the latter actually enforces the setting as if it was manually set by the user.

Also do note that preferences set using defaultPref() will not be highlighted in about:config.

A practical example with defaultPref() and pref()

Say I wanted to disable WebGL. I could simply do as we've done so far.

defaultPref("webgl.disabled", true);

However, say I wanted to keep WebGL disabled most of the times, but occasionally needed to re-enable it to make certain websites work.

With the previous solution, I would have to turn it on, and then, once I'm finished, remember to turn it off manually, otherwise it would remain enabled indefinitely (because defaultPref() wouldn't override my user preference).

Alternatively, I could use pref()

pref("webgl.disabled", true);

This way, I could still turn on WebGL as needed, but, even if I forgot to turn it off again, it would be disabled next time I launch the browser.