Safari and super slow after Big Sur update

Just updated to Big Sur few days ago and have the same issue. Restarting with cmd+opt+P+R helped but not for long. It lasted a day and both browsers, Safari and Chrome as very slow. Did anyone solve this issue yet? Hope Apple is looking into it.

I have the same problem after a week having my new MBP16 although on i9, 32GB RAM, 1TB NVMe and AMD5500 4GB. I found that this solution helps me without having to reset NVRAM.

"Changed mine to Google Open DNS numbers 8.8.8.8 and 8.8.4.4. Kept a copy of original server numbers in case of any problem."

I just changed the DNS to Google DNS. Link to the original post:https://discussions.apple.com/thread/252111914?answerId=254552857022#254552857022

I'm having this problem too on several Macs, but sporadically. I've noticed that when it occurs, that umount appears in the Activity Monitor spiked at 100% cpu. I am unable to kill the process even with force quit or kill -9. After the process eventually crashes, safari goes back to normal.

If anyone else is still experiencing this issue, can you check your activity monitor to see if umount is running?

I'm having this problem too on several Macs, but sporadically. I've noticed that when it occurs, that umount appears in the Activity Monitor spiked at 100% cpu. I am unable to kill the process even with force quit or kill -9. After the process eventually crashes, safari goes back to normal.

If anyone else is still experiencing this issue, can you check your activity monitor to see if umount is running?

I have the same problem. Safari is really slow, especially compared to other browsers and especially with javascript, even common/simple sites YouTube I get the "this page is using significant energy"...

Has anyone found what is causing this. For me, since I updated to Big Sur. half the time when I just go to bookmarks or try to add a bookmark Safari hangs. I've tried reinstalling the OS, clearing caches, was already using google dns, ditching all my extensions, and doing a NVRAM reset. Nothing has worked. I am ready to reload my backup and ditch Big Sur. I figured by now all the problems would be solved.

Same problem here. I have tried several approaches but Safari 14 is still very slow in MacBook Pro 2018 with Big Sur.

It's not just on Big Sur. Updated from 13.xx to 14.xx (running mojave on my dev mac). What a mistake! Super slow, can't cope fps when 2 windows are open. If sounds are playing, they are reduced to noise. Webgl runs fine but as js is no longer updating the shaders/logic on time, it's not usable anymore, especially when you must have multiple windows open to test a multiuser program.

Is there an archive with older versions installers somewhere? I'd like to try a few versions back from this unusable 14.2 to pick the best till the 13.5 I have on backup.

This bug has resulted in daily headaches on an 8GB M1 to the point of making it unusable to run anything else simultaneously. I understand the Apple yearly release, but it is absurd that this bug, clearly clearly a reproduce-able bug, has simply been something we are expected to deal with, for a year. C'mon make a hot-fix when your stuff is sooooooo broken. I stopped using Safari completely, except, you know all my passwords, bookmarks and auto-fill data are there, plus airplay only works from there.... So it's open all day anyway. Get it together please.

Ok so turns out, I had both safari 13.x and the preview 13.1 installed before updating safari to 14.x

I now have the preview as main browser and I can work again. What a difference!!

When I run both at same time, for same tasks, I see 14.x failing royally on almost everything. Not only slow in general, fps rate not respected, js slower, html refresh on dynamic/css animated sites is ridiculous, noisy sounds etc.. Busy with a SignalR multiuser 3d game atm, I see in preview I can play smooth with 4 users in four windows open, all with debug on. All traces updated as expected just like in the previous release version I had. The 14.2 already have issues with 2 windows open, and fps goes down from steady 60 to a jumpy 30-40. Fans are going so hard my mac could take off.

More disturbing, before making the preview my default browser, got 2 reports of sites that "failed" in 14.x. Like USPS.com where I was trying to track a package. No error in console, just that plain stupid and useless "A problem repeatedly occurred with [address]" with no details as on iOs ( Apple, please trace the error (if any), as some of us want to know what's wrong exactly). The same page, loads fast with zero issue in the preview 13.1, no error, no warning.

Basically now with both running side by side on same machine, it's clear this browser version is so bad it should never have been released.

PS: Apple, while you fix this abomination, could you also remove these insanely annoying energy warnings please? At least give us the choice to disable them for a given page.

Hey, this is funny. I had big troubles with my apple ID after updating on BigSur. My Mac, iPhone, Watch, are signed in to the same Apple ID, but all devices showed: the service could not be activated because you are not signed to the same Apple ID. I need to sign out from iCloud on all devices and sign in again. It helps. But the Safari is ugly. The only help for me is to migrate to Chrome for a while.

The latest update of MacOS (11.6) just rendered Safari totally unusable.

Having the same problem with Safari. I've narrowed it down to an issue with javascript (pages that use a lot of java cause major slow downs.) But I don't know how to resolve it. Any ideas?

TLDR; Try disabling Time Machine or removing faulty Time Machine targets.

After working on this for awhile, I think I've figure out what's causing the issue that I'm seeing with umount and Safari. Each time that umount is stuck and Safari is non-responsive, Time Machine was failing to access a disk over the network. I've seen it both with a Synology Time Machine share and a Mac OS Server Time Machine share. Removing the faulty Time Machine target or disabling Time Machine altogether appears to result in the issue no longer happening. I hope that this helps at least some of you.

I have the same problem: Update to of MacOS (11.6) just rendered Safari totally unusable. Safari was slow before, but now I have to close and open it every 2 minutes.