Blog about software development


Firefox wont load and/or uses high CPU

13 Jan 2022 - by 'Maurits van der Schee'

Firefox has a bug in its HTTP3 implementation causing the browser to hang or use a lot of CPU. You can temporarily disable HTTP3 as a workaround for the problem. You need to go to "about:config" and set "network.http.http3.enabled" to "false". In this post I'll show you how to do this using a script on Linux.

On Linux

Disable HTTP3 (as a user preference):

echo 'user_pref("network.http.http3.enabled", false);' | tee -a \
$(find ~/.mozilla -name prefs.js | sed "s/prefs/user/g" | xargs)

Revert disabling HTTP3:

sed -i "/network.http.http3.enabled/d" \
$(find ~/.mozilla -name prefs.js | sed "s/prefs/user/g" | xargs)

You need to execute the script when Firefox is not running.

I hope this helps.

NB: I have heard people report that this bug is now resolved, so updating to the latest version might solve the problem as well.

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