Firefox's protection against fingerprinting

Firefox Firefox Last updated: 10/01/2023 55% of users voted this helpful

Like other browsers, Firefox’s functionality is influenced by your operating system, hardware, graphics cards, additional software, and even the fonts you install. Some website technologies, like HTML5 Canvas, can even uniquely identify you based on how your computer draws images.

Some websites, particularly those using HTML5 Canvas, look at this unique combination of factors and assign you a number, or a “fingerprint”, which makes you identifiable across the Web. This “fingerprint” is potentially used to profile you for targeted content without the use of cookies. Firefox already has an Enhanced Tracking Protection feature that blocks a list of known "fingerprinters" when your privacy settings are set to Standard (the default) or Strict. Fingerprinting Protection is a different, experimental feature. It is likely that it may degrade your Web experience so we recommend it only for those willing to test experimental features.

How am I protected?

If a website tries to extract your data, Firefox will warn you with a prompt in the address bar. You can choose whether to allow the website to extract your data. This is the most common way to observe this protection.


However, the Canvas Permission Prompt is not the only thing that Fingerprinting Protection is doing. Fingerprinting Detection changes how you are detected online:

  • Your timezone is reported to be UTC
  • Not all fonts installed on your computer are available to webpages
  • The browser window prefers to be set to a specific size
  • Your browser reports a specific, common version number and operating system
  • Your keyboard layout and language is disguised
  • Your webcam and microphone capabilities are disguised
  • The Media Statistics Web API reports misleading information
  • Any Site-Specific Zoom settings are not applied
  • The WebSpeech, Gamepad, Sensors, and Performance Web APIs are disabled
This is not an exhaustive list - other features may be altered or disabled.

How do I enable or disable this protection?

  1. Open Firefox: Launch your Firefox browser on your computer.
  2. Access Settings: In the Menu bar at the top of the screen, click Firefox and then select Preferences or Settings, depending on your macOS version.Click the menu button Fx89menuButton and select Settings.
  3. Navigate to Privacy & Security: In the left-hand sidebar, click on Privacy & Security.
  4. Customize Enhanced Tracking Protection: Scroll down to the "Enhanced Tracking Protection" section.
  5. Enable Fingerprinting Protection: To enable Fingerprinting Protection, select the Custom option from the Enhanced Tracking Protection settings.
  6. Adjust Fingerprinting Protection Settings: Once you've selected Custom, you will see options to block Known fingerprinters and Suspected fingerprinters. Check the boxes next to these options to enable them. Additionally, you can choose whether to block Suspected Fingerprinters in all windows or just in private windows using the dropdown menu located on the right-hand side of this option.
    Fingerprinting protection
  7. Disable Fingerprinting Protection: To disable Fingerprinting Protection and return to the default settings, simply select "Standard" or "Strict" under the Enhanced Tracking Protection section.

Currently, Fingerprinting Protection is an experimental feature enabled by a confirmation flag set in about:config. It can also be enabled by Web Extensions.

Warning: Changing advanced preferences can affect Firefox's stability and security. This is recommended for advanced users only.

  1. Type about:config in the address bar and press EnterReturn.
    A warning page may appear. Click Accept the Risk and Continue to go to the about:config page.
  2. Search for privacy.resistFingerprinting and set it to true. You can double-click the preference or click the Toggle Fx71aboutconfig-ToggleButton button to toggle the setting.

If it is bolded and already set to true, you, or an extension you installed, may have enabled this preference. If you discover the setting has become re-enabled, it is likely a Web Extension you have installed is setting it for you.

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