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Firefox seems to report to websites that I am running windows 10, while I am actually running macOS.

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  • Last reply by cor-el

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Firefox seems to report to websites that I am running windows 10, while I am actually running macOS. This mostly isn't a problem, but sometimes websites will only produce download links for the OS your browser reports, without giving me the option to click the mac download manually. Is this an option I can configure somewhere? Is this coming from the fingerprinting prevention?

Chosen solution

Do you have the privacy.resistFingerprinting preference set to true? This setting can change the user agent and cause this type of issue.

If it's set to true try changing it back to false and restart Firefox.

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Your user agent (the thing that tells websites about your system) says Mozilla/5.0 (Windows NT 10.0; rv:68.0) Gecko/20100101 Firefox/68.0.

Obviously a program is modifying that information. Try the steps in the How to reset the default user agent on Firefox article to see if that helps fix the issue.

There are some security programs that can change the user agent as well.

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Understood, I see the user agent data is the problem. However, I was unable to follow the steps to reset the default user agent because the configs the linked how-to described did not show up on my search. When I search 'useragent' in about:config I get the following configs, screenshot attached. I'm on Firefox 75.

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Chosen Solution

Do you have the privacy.resistFingerprinting preference set to true? This setting can change the user agent and cause this type of issue.

If it's set to true try changing it back to false and restart Firefox.

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That was it. It is interesting that resist fingerprinting would conform the user agent to a specific value like that, isn't one consistent value just as arbitrarily selected as another? Thanks very much.

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I added this solution to the How to reset the default user agent on Firefox article and included a link to the Firefox's protection against fingerprinting article, which explains this feature.

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Note that "Resist Fingerprinting" also changes the browser version in the user agent to the current ESR release (Firefox 68) and sets the timezone to UTC.

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