https://support.mozilla.org/en-US/kb/firefox-protection-against-fingerprinting

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 1. Home
 2. Firefox
 3. Protect your privacy
 4. Tracking protection
 5. Firefox's protection against fingerprinting

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        [*] Firefox
        [Version 99 ]
        [Windows 8      ]

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[2020-]
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Firefox's protection against fingerprinting

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 Protectiona Content Blocking
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 under
heavy development in Firefox. 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.

fingerprint promptFx75-HTML5Canvas

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?

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 see if it is bolded
    and set to true. If so, you, or an extension you installed, has
    enabled this preference. You can double-click the preference or
    click the Toggle Fx71aboutconfig-ToggleButton button to toggle
    the setting.

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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These fine people helped write this article:

AliceWyman, Wesley Branton, Joni, tomrittervg, user1632815
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