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Mozilla engineers discovered a bug in Windows Defender which causes CPU usage to be high when running Firefox (and other browsers too).

We've reported the issue to Microsoft, and apparently a fix is going out soon (it's currently in the beta version of Defender).

We're seeing a ~75% CPU usage reduction with this fix when running Firefox (on YouTube, in this case).

So Windows users: if you want better CPU usage, make sure that you're applying Defender updates.

Details: https://bugzilla.mozilla.org/show_bug.cgi?id=1441918#c91

1441918 - Antimalware Service Executable (Windows Defender) very active / high CPU when using Firefox

RESOLVED (nobody) in External Software Affecting Firefox - Other. Last updated 2023-03-31.
bugzilla.mozilla.org
in reply to Paolo Redaelli

mhoye
mhoye
• •
@paoloredaelli That approach works for privileged individuals, but for developers it means opting out of 95%+ of the market. Only a small fraction of computer users get to choose their platforms, for a bunch of different reasons, and we need to meet people where they are if we're going to help them.
@Paolo Redaelli

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