Some web based games laggy since Firefox 148

Hi gully,

The following article might help you with performance-related issue like this Fix Firefox using too much memory or CPU resources .

Can you check and see if it help?

You mean this https://support.mozilla.org/en-US/kb/firefox-uses-too-much-memory-or-cpu-resources? That didn't help. I should mention the issue occurs even on a new Firefox profile. Hence why I debugged way down to v147.

And just to confirm — you've restarted into Troubleshooting Mode as well to rule out any performance tweaks or GPU optimization impacts?

Would you be willing to actually help point at a particular build that changed this for you?

If it's rather easy or early on in the game for you to recognize good vs. bad state quickly and knowing that e.g. 148 is bad and 147 was definitely good, you can run mozregression to help pinpoint the exact moment in versions this changed for your timeline — it'll serve the intermediate builds for you one by one to try and evaluate, and clean up after itself when it finishes.

I opened in Troubleshooting mode and the first game threw an error "Your browser does not support WebGL". I am not sure which build began this issue, I just run separate binaries from 146-149 with AI help. Testing new profiles with each game (only adding ublock origin). Firefox 147 and below play fine, no lag. 148 to 151 lag and stutter and increase the ping considerably.

Ah, so it needs the full acceleration enabled, gotcha:/

If you ever have the time and mood to help find out the exact build out of the, say, 60–80 that might be in that 148–149 range, it would be greatly appreciated. The tool I linked above has a GUI for Linux too (should have Ubuntu tarballs so expect no issues for Mint) and you just tell it the version range and it will help bisect down the issue by pulling development builds from that period, and you just say "good" or "bad", to figure out the next one to try, to help land on a day, and then on a patch, that changed the behavior.

It may even land on an issue that's already tracked so you'll know what to follow for future changes.

Actually, speaking of which — what does your about:support say about "WebRender"? Could that be https://bugzilla.mozilla.org/show_bug.cgi?id=2043249 related?

Also instead of going back in time, you might wanna check how Nightly nightly.mozilla.org performs — to see if there was a bug, whether it's not actually already fixed? That would also help to verify. Thanks!

Thank you everyone for your comments. With painstaking work to debug with a lot of help from Gemini AI (command `mozregression --good 147 --bad 148 --background-dl-policy cancel --pref gfx.webrender.all:true --addon ~/Downloads/ublock_origin-1.71.0.xpi`), I arrived at this result https://hg-edge.mozilla.org/integration/autoland/pushloghtml?fromchange=9de2a5e939e2632e5a96228e95f61eafdd2ef1fa&tochange=5bec6eddfbe9802b1d82b603a05a49051f7104ce.

From Gemini:

"I ran mozregression to trace the sudden heavy performance lag in this WebGL game. The tool isolated the regression down to Bug 2002635 ("Disable asm.js") which landed between Dec 18 and Dec 19, 2025. Because the asm.js optimization pipeline was disabled/removed by default in Firefox 148, the game's code is no longer being compiled optimally, causing heavy stuttering and frame drops."

I am not sure if the two games use asm.js, but I confirmed from other players and they have all switched to Chromium based browsers due to the lag/stutter.

https://hg-edge.mozilla.org/integration/autoland/pushloghtml?fromchange=9de2a5e939e2632e5a96228e95f61eafdd2ef1fa&tochange=5bec6eddfbe9802b1d82b603a05a49051f7104ce

javascript.options.asmjs

That helped. The chrome mask didn't. I assume I should email the games developer with this instruction websites should recompile their games to WebAssembly

Yes, it would be nice.