iMac slows down after Big Sur installing

I just replaced a 2013 iMac running Catalina with a late 2019 iMac and installed macOS Big Sur. It is unbelievably slow. Boot time painful but that's only once a day so I could live with that, but almost everything you do on the iMac is painfully slow - even loading System Preferences! Safari is the worst of all - pretty much unusable so I have switched to Chrome which is a little better.
If the WiFi card hadn't failed on my 2013 iMac I would go back to it immediately. Hard to fathom how a 6+ year newer iMac can be so massively slower or how Apple could treat its loyal customers with such disrespect. Big Sur should be renamed Big Slow.

I can't user Xcode and other softwares because each program so so so slowly loading. The storages is enough. 

Mac (Retina 4K, 21.5-inch, 2017)
Serial number: DGKTRHJ5J1G5

Using a tip from someone else on this board, I sped my Big Sur OS about 10X by simply creating and then exclusively using a new user my macbook. Evidently the old user brought a lot of old baggage with it.

Imac (Retina, 27-inch, Late 2014)

4 GHz quad core Intel Core i7
32 GB 1600 MHz DDR3
Amd Radeon R9 4GB

The same problem here with Big Sur. It was ok for 3 month. Then 3 days ago, without reasons, it started taking too long to start up the computer, and every time i want to do something simple like a new folder, it takes between 5 min. to do it. Black screen on start up, and after put the password i can see my desk only after almost 10 minutes. It's very painful. I've tried everything but nothing helped. It seems like some process doesn't working. Apple do something now!!

Same here on a 2017 iMac with fusion drive. Upgraded to Big Sur on November. Since then every time it needs to take several minutes for the computer to boot into the login screen. After typing the password, the computer takes another several minutes to load into desktop before I can successfully open the first app.

The time to startup the Mac is much longer than using Catalina. Hope this issue can be fixed soon.

Same here, I updated my Mac which I purchase on 2017 and was sold a 2015 so be careful... and they then make us update and then my computer is acting stupid. Slow as **** and they say it my fault. When its clear they are responsible of this problem. My computer isn’t full at all I have so much space and I did everything they’ve been asking and now they get to just clean there hands?

What a mistake. My MB PRO is spinning for a few hours to open a web browser. I have to go back to Catalina. Is there any way to go back without data loss?

I have an iMac 2014 5k with 32 GB Ram, The system can't manage the memory. most of the time I have 4.3% to 12% free memory. And the speed is so low for simple tasks.

If I can help somebody I just would recommend NOT to install Big Sur, again, if you have doubts DON'T DO IT, it will tear apart your mac/iMac

I have an iMac Late 2014 with 32 GB RAM and 1TB SSD hard drive that worked perfectly until I updated to Big Sur

Things that happened after installing big sur:

• OS Boot delayed: From 10 seconds to more than 30, some times even more than 1 minute

• Terribly slow: After Big Sur, opening just one program slows the computer, now I can't use iMovie and any other software because the computer collapses

• Permissions issue: After updating I had several issues with permissions, I couldn't write to folders I did and more important, I couldn't use the System Preferences because it said my user wasn't admin, I've been using the same user for more than 6 years.

My iMac is utterly unusabled since the Big Sur updated. It can't handle simple daily tasks like coding and emails without grinding to halt, and takes about 10 minutes to reboot after it crashes.
Great work Apple this is the worst update in history, you have surpassed Microsoft finally at something.

I especially love the fact you've brought back that old feature favourite 'the spinny wheel of death'!! I'm equally impressed by the general OS responsiveness that puts catatonic mummified pharoe's to shame.

I've experienced problems with endless lags and the spinning wheel with Mail (when trying to quit), Safari (when trying to open a new tab via keyboard) and other apps when trying to quit and also when trying to start them. The issue is really annoying since the only solution seems a long press to the power button to switch off the unit.

The update to 11.2 and 11.3 beta didn't solve the problem. Sometimes the problem disappears for several hours and then returns again on both my iMac 2019 and my MBP M1 2020.

Same problem here. I had Sierra OS 10.12.6 and it worked beautifully. But I needed to installed Office 365 so had to update. Called Microsoft and they walked me through the update and they chose BigSur. What a mistake. It is soooooo slow plus I have to keep putting in passwords and getting texts to verify. What a pain. How dumb of Microsoft, full knowing that there were problems with this update. I could have done Mojave or Catalina.

Now what do we do, are we stuck with this update and can we downgrade?

2017 Macbook Pro 15" was running fine with Catalina. Big mistake to upgrade to Big Sur, everything went south since. Computer is very slow, I see the spinning wheel a lot. Very hard to work like this

Hi,
I have been using MacBook Pro 2016 since 17-07-2017 without any problem. Suddenly a week ago (feb-2021) a problem appeared with its screen, that it turns off after 40-45 degree extension. I checked it on Apple site and found it is a common problem called Flexgate problem and my Mac version is involved.

Now i am using it on external screen because official Apple service in Erbil, Iraq declined to fix.

I also updated it to Big Sur and have two other problems with it: first, apparently the Mac has gotten slower in its processing which is bothering. Second, i was forced to use google chrome instead of safari which i preferred before, because safari does no longer load any web page (not even google search).

This is about my Mac:
MacBook Pro
2 GHz Dual-Core Intel Core i5
8 GB 1867 MHz LPDDR3
Macintosh HD
Intel Iris Graphics 540 1536 MB
C17SN40DGVC1

Kind regards,
Reben Darweesh

Same here! macbook pro 2017 non TB
I need to solve it or I have to go back to Catalina.