1871595 - navigator.userAgent reports Intel cpu on macs with arm processors

Status: RESOLVED WONTFIX

(Core :: Networking: HTTP, defect)

Description

[Steven Fusco]

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:121.0) Gecko/20100101 Firefox/121.0

Steps to reproduce:

I called navigator.userAgent

Actual results:

it returned "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:121.0) Gecko/20100101 Firefox/121.0"

Expected results:

I have an Apple M1 Pro macbook, it should not say "Intel" and should instead say aarch64 or arm or something else.

Comment 1

[Tooru Fujisawa [:arai]]

To my understanding, it's intentional, in order to reduce the fingerprinting possibilities (e.g. bug 1520419 comment #2 for version number part).
Safari also reports "Intel Mac OS X" on M1.

Comment 2

[Sunil Mayya]

Hey Tim,
Could you please confirm if this is expected here?

Comment 3

[Chris Peterson [:cpeterson]]

This is expected behavior and consistent with Safari's and Chrome's User-Agent strings on ARM64 macOS. Revealing the actual CPU architecture can cause compatibility issues for websites that don't expect the User-Agent string to change. That's why the User-Agent string still reports the old "Mac OS X 10.15" name and version, even on macOS 14.

Is there a use case for revealing ARM64 to websites? If a website is, for example, hosting macOS software, they can offer Universal binaries that support both Intel and ARM64 or offer separate links for the user to choose.

Comment 4

[Ed Guloien [:edgul]]

I'm going to close this. If someone knows valid use-case for this, we can re-open.