I tested by visiting every tab in this window, 14 of which hadn't been loaded yet after the Firefox 92 update. CPU use went to 100% for maybe 10-15 seconds, and then returned to baseline. Here's the graph:

Of course, the strain probably depends on the specific pages involved, but I'm not getting a hair-on-fire three-exclamation-point feeling about this.

[quote] But I'm not getting a hair-on-fire three-exclamation-point feeling about this. /quote

What do you mean? This is not normal, 6 tabs shouldn't load so slowly and shouldn't max whole i5 9600KF!!! I used to open on Chrome hundreds of tabs at start and it took just couple seconds... 6 youtube tabs BTW.

Start Firefox using Troubleshoot(Safe) Mode {web link}

A small dialog should appear. Click Start In Troubleshoot(Safe) Mode (not Refresh). Is the problem still there?

https://support.mozilla.org/kb/Firefox+is+already+running+but+is+not+responding

https://support.mozilla.org/en-US/kb/firefox-slow-how-make-it-faster

https://support.mozilla.org/en-US/kb/firefox-uses-too-many-cpu-resources-how-fix

https://support.mozilla.org/en-US/kb/firefox-uses-too-much-memory-ram

https://support.mozilla.org/en-US/kb/firefox-hangs-or-not-responding

This is not normal, 6 tabs shouldn't load so slowly and shouldn't max whole i5 9600KF!!! I used to open on Chrome hundreds of tabs at start and it took just couple seconds... 6 youtube tabs BTW.

How slowly? It's possible that Firefox can't load YouTube from cache and needs to retrieve the pages again. I generally don't keep YouTube tabs open, so I don't have a reference point for that, just the test results I gave you.

Start Firefox using Troubleshoot(Safe) Mode {web link} A small dialog should appear. Click Start In Troubleshoot(Safe) Mode (not Refresh). Is the problem still there? https://support.mozilla.org/kb/Firefox+is+already+running+but+is+not+responding https://support.mozilla.org/en-US/kb/firefox-slow-how-make-it-faster https://support.mozilla.org/en-US/kb/firefox-uses-too-many-cpu-resources-how-fix https://support.mozilla.org/en-US/kb/firefox-uses-too-much-memory-ram https://support.mozilla.org/en-US/kb/firefox-hangs-or-not-responding

As I said: I tried troubleshooting mode already - same problem :(

empleat said

This is not normal, 6 tabs shouldn't load so slowly and shouldn't max whole i5 9600KF!!! I used to open on Chrome hundreds of tabs at start and it took just couple seconds... 6 youtube tabs BTW.

How slowly? It's possible that Firefox can't load YouTube from cache and needs to retrieve the pages again. I generally don't keep YouTube tabs open, so I don't have a reference point for that, just the test results I gave you.

Extremely slowly: it takes couple seconds. Besides even single tab cause CPU usage go to 80% and loads like 3 seconds.. While 6 tabs like 6 seconds.

Maybe it's this bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1724980

Can you try to test it in the Nightly version?

On nightly usage is slightly less: 60-80% but tabs open still slowly!!! What is that bug BTW? I don't see solution there!

92.0.1 problem still exists, any ideas ???

Hi empleat!

How many browser extensions/add-ons do you have? Can you list them? Many interact with YouTube so it's possible one is the culprit.

Side note: I'm not surprised YouTube links are loading more quickly in Chrome. Google owns both and I have a feeling YT is integrated into Chrome by default (aka, it preloads video DLLs). This is all speculation though, I haven't tested.

Hi empleat! How many browser extensions/add-ons do you have? Can you list them? Many interact with YouTube so it's possible one is the culprit. Side note: I'm not surprised YouTube links are loading more quickly in Chrome. Google owns both and I have a feeling YT is integrated into Chrome by default (aka, it preloads video DLLs). This is all speculation though, I haven't tested.

Nope that's not it! I tried nightly build = same issue, also clean boot, start Firefox in troubleshooting mode, general tips on Firefox support site for high cpu usage, safe mode networking. No background programs! I Am now on FF 92.0.1 - same issue!

Slowness is not exclusive on youtube unfortunately and tabs load very slowly, just 6 tabs maxes CPU on 100% while they load slowly....

Can you post a comparison screenshot of the Windows 10 Task Manager Performance tab showing the performance with restoring your tabs? For reference, mine was attached to this reply: https://support.mozilla.org/en-US/questions/1349711#answer-1441369

OK.....

Thanks. Looks like about 15 seconds of higher CPU utilization to restore 6 tabs with a brief spike to 100%. With my slower system, restoring 14 tabs caused a much longer spike to 100%.

I don't know what is involved in restoring a tab, so I don't have an opinion on whether this is reasonable. Do you want to file a bug report? https://bugzilla.mozilla.org/

Yeah probably should do that. zzzzzzzzz...

Thanks. Looks like about 15 seconds of higher CPU utilization to restore 6 tabs with a brief spike to 100%. With my slower system, restoring 14 tabs caused a much longer spike to 100%. I don't know what is involved in restoring a tab, so I don't have an opinion on whether this is reasonable. Do you want to file a bug report? https://bugzilla.mozilla.org/

Bugzilla says: it is not a bug, after checking a profile record. Hmmm... It is strange, because I Am using 2 Mozilla instances, it was happening in both (including one with small amount of tabs) but now since v 93.0, it doesn't happen there. However it is still happening in my main instance! But even in instance, when it doesn't max CPU to 100%, 6 tabs cause still 53% CPU usage, which doesn't seem great, at least they load instantly!

Now issue doesn't happen with only 6 tabs in my main window, while it was previously happening in 3 different profiles of Firefox! That is after Firefox 93.0. But performance in my main windows where I have 800 tabs is still piss poor. It used to be fine with 1000 tabs... So I Am leaving Firefox, I can't work like this sadly...

Part of the problem may be your internet service provider. Opening multiple tabs can create an overload on your downloaded data via the ISP, especially if you use satellite service.

How would that be related to 100% CPU usage, besides I have 150mb/s cable! Never had problems with my ISP over 10 years!

My apologies for attempting to help. It won't happen any more. Have a great day and good luck.

My apologies for attempting to help. It won't happen any more. Have a great day and good luck.

LOL you are crazy. I merely said that is not problem. OK I will lie and talk to you next hour about imaginary problem. What Am I supposed to say.

Today people are so sensitive, we are just talking facts... I don't understand what is going oN?