Mozilla omits CPU architecture information from Firefox's user agent

[harlan4096]

Mozilla plans to omit CPU architecture information from Firefox's user agent and several supported APIs to reduce the digital fingerprint of Firefox users.

Web browsers reveal information automatically to websites that users open in the applications. The user agent reveals information about the browser and browser version, operating system, and, up until recently, also the CPU architecture.

Fingerprinting scripts use user agent information and other information, e.g. language and location, to create digital fingerprints. The accuracy of fingerprints increases with the number of unique data points.

Firefox won't reveal one of the information bits to scripts and sites anymore going forward. The change, implemented already in recent Firefox Nightly 69 builds, omits CPU architecture information from the user agent.

Firefox used to differentiate between the following CPU architectures:

1. 32-bit Firefox on 32-bit operating systems.
2. 32-bit Firefox on 64-bit operating systems.
3. 64-bit Firefox on 64-bit operating systems.

Firefox users who run Firefox 69 will notice that scripts that return the user agent won't differentiate the information anymore. A simply Google search for check user agent reveals that as seen on the screenshot below.

The current Nightly version of Firefox run on a test system returns the following user agent:

Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:69.0) Gecko/20100101 Firefox/69.0

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