Chameleon for Firefox: user agent and data spoofer

Chameleon is a new open source extension for Mozilla Firefox that is a port of the Firefox add-on Random Agent Spoofer for the browser.

Random Agent Spoofer added options to Firefox to spoof the user-agent and other information that the browser leaks to websites and servers on connect. The add-on is not compatible with Firefox 57 or newer, and Chameleon brings most of the functionality to Firefox 57 or newer devices.

There are plenty of things that you can do to modify a browser's fingerprint; sites and companies may fingerprint browsers using data that the browser reveals automatically or when scripts are executed.

Note: Chameleon is not related to the Chrome extension Chameleon with is also an anti-fingerprinting extensions.

Chameleon for Firefox

Chameleon focuses on modifying the user agent of the browser. Firefox reveals the user agent to sites and servers when it connects to them. The user agent reveals the browser and version, operating system, accepted languages, referrer, and other information to sites.

The extension's core focus is the user agent but it provides options to change headers and configure other privacy related options next to that.

As far as the user agent is concerned, the following options are provided:

• Set a random user agent (mobile and/or desktop)
• Set a random desktop user agent.
• Set a random mobile user agent.
• Set a specific user agent. Supported are browsers for Windows, Mac OS X, Linux, Android, and iOS.
• Set a custom user agent.

You can make one-time changes to the user agent or configure the extension to change the user agent periodically. Available time intervals range from changing the user agent every minute to every hour; there is no option to change it less frequently, for example every six hours or once a day.

Chameleon comes with a big list of preset user agents. You can set the user agent to various Chrome, Firefox Microsoft Edge or Internet Explorer versions on Windows alone.

The user agents are necessarily up to date. The Firefox user agents are based on Firefox 59 even though Firefox 60 is already out. An option to set the user agent to the "real profile" is provided as well. The option can be useful if sites refuse to work with spoofed user agents.

Chameleon supports other browser header modifications and privacy options. When you switch to headers in the interface, you get the following options:

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• Disable Authorization.
• Enable Do-Not-Track.
• Spoof if-none-match (ETAGs).
• Spoof via using a custom or random IP.
• Spoof X-forwarded-for using a custom or random IP.
• Disable Referer.
• Spoof Source Referer.
• Set Referer X Origin Policy.
• Set Referer Trimming Policy.
• Spoof Accept Encoding.
• Spoof Accept Language.

One issue that you may run into when configuring the headers options is that no explanation is provided. While it is easy enough to understand some options, Enable Do-Not-Track does exactly that, it is unclear what others like Disable Authorization or Spoof via do exactly.

A switch to the options tab displays another list of privacy related preferences that you may configure to your liking or needs.

To name just a few options:

• Disable WebSockets.
• Enable Script Injection.
• Protect window.name.
• Spoof the screen size.
• Enable tracking protection.
• Enable first-party isolation.
• Resist fingerprinting.
• Customize cookie behavior.
• Set several options in about:config using direct links, e.g. disable Pocket, Battery API, DRM, Device Sensors, or PDF.js, and several reporting options.

The browser extension supports a whitelist using a specific profile for use on sites. It is ideal for use on sites that don't work with spoofed profiles.

Comparison with Random Agent Spoofer

Chameleon supports most of the features that Random Agent Spoofer supports but there are differences. Random Agent Spoofer includes a larger set of user agents, e.g. Game Consoles or validators, and it supports more spoofing and privacy features such as spoofing accepted documents.

Most features, the core features, are supported on the other hand. Some suffer from WebExtension limitations such as the inability to modify about:config options directly.

Closing Words

Chameleon is an interesting option for Firefox 57 and newer users who used Random Agent Spoofer in the past or want to spoof the user agent and modify a large set of privacy related options in the browser.