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How is the useragent is set

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  • Last reply by cor-el

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How does firefox determine the user agent? I'm especially interested in how the operating system is detected. Is there a way to manipulate the detection?

How does firefox determine the user agent? I'm especially interested in how the operating system is detected. Is there a way to manipulate the detection?

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Hi, you may find what is listed in Google search using your question enough information : https://www.google.com/search?q=How+does+firefox+determine+the+user+agent%3F&ie=utf-8&oe=utf-8&client=firefox-b

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Note that it not only the user agent, but there are more navigator properties.

The user agent is send via the HTTP request headers, but JavaScript running on a page can detect more. There are override prefs for most of these, some examples:

  • general.useragent.override
  • general.platform.override

Note that some properties are spoofed when Resist Fingerprinting is enabled.