Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.

SamPotts

macrumors 6502
Original poster
Sep 25, 2010
278
59
Sydney, Australia
Does anyone know why `com.apple.quicklook.ThumbnailsAgent` would be constantly consuming CPU and perhaps how I can fix it? It's not a huge amount but it just seems to be running needlessly, like it's stuck in a loop and it also brings `diskarbitrationd` along for the ride. It's been running since I upgraded to Big Sur (a day after release). I've tried clearing the quick look cache. I even tried disabling it but that doesn't seem to work on Big Sur.
 

BigMcGuire

Cancelled
Jan 10, 2012
9,832
14,028
Now I'm having this... Was wondering why my fan was running all the time.

Thumbnails agent and disarbitrationd using a good chunk.

Did you ever find out what it was?
 

BigMcGuire

Cancelled
Jan 10, 2012
9,832
14,028
I notice I get this if I pull my external drive out without ejecting it. And soon as I reconnect it, CPU usage goes back to normal.

Between this and Apple Notes using high CPU - also getting stuck on CPU drain....


Ok, just did a test - ejected my external as I should -- no CPU usage and no disk arbitration, interesting.
 

Sooby

macrumors member
Apr 5, 2019
61
38
I've just had this problem as well. The 'com.apple.quicklook.ThumbnailsAgent' was causing my iMac's fans to run high. I force quit it in Activity Monitor and it lowered the CPU usage and fans went right back down.
 

BigMcGuire

Cancelled
Jan 10, 2012
9,832
14,028
I definitely have not found a solution. Every now and then this causes my MBP fans to run. Usually after a small amount of file copying. Ends after a few mins. Never happened before on previous Mac OS versions. :/
 

BigMcGuire

Cancelled
Jan 10, 2012
9,832
14,028
1615388409042.png


Chugging away like crazy. sigh. I let it run for a good 30 mins then killed it.
 

BigMcGuire

Cancelled
Jan 10, 2012
9,832
14,028
Still having problems with this always being the highest CPU consuming app. I'm getting ready to just fresh install Mac OS again.
 

BigMcGuire

Cancelled
Jan 10, 2012
9,832
14,028
I have the same problems for a few months now, I always manual disable it, haven't tried the iCloud option yet,
let us know how that works out.
How do you manually disable it? (killing the service in activity monitor?).

Will do - my MBP 13' is half way done re-downloading my iCloud after almost 3 hours of doing this, lol. Once downloaded, I'll restart - may have to do a day or two of work - but will keep an eye on activity monitor.
 

BigMcGuire

Cancelled
Jan 10, 2012
9,832
14,028
Well it downloaded all my iCloud files --- no thumbnail agent - I've restarted a few times. I'll keep an eye on it. Looks like that may have done it. I just went to Settings --> Apple ID - and unchecked iCloud Drive - waited for that to process - then rechecked. Fingers crossed!

May just be me but I'm noticing an overall OS speed increase after this. <sigh>.
 
Last edited:

BigMcGuire

Cancelled
Jan 10, 2012
9,832
14,028
Still hasn't come back. Looks like that solved it. Will report here if it does come back. I'll give it a few days before I say I'm certain.
 

BigMcGuire

Cancelled
Jan 10, 2012
9,832
14,028
1617594478553.png


And it's back. Sigh. I guess I should really do a clean OS install. I'll let this run for a day and see if it goes away.
 

Manuphoto

macrumors newbie
Apr 4, 2020
11
19
Montreal, Canada
View attachment 1753698

And it's back. Sigh. I guess I should really do a clean OS install. I'll let this run for a day and see if it goes away.
I got the same issue. Logging out from iCloud didn't help. I can't say it really slows my M1 Mac, but it is annoying. The weird thing is that sometimes it stops by itself... and then restarts. Ejecting external drive has no impact. Anybody has a durable solution for this? I've seen threads about this on at least three different macOS iterations so it's not only Big Sur.
 

BigMcGuire

Cancelled
Jan 10, 2012
9,832
14,028
I got the same issue. Logging out from iCloud didn't help. I can't say it really slows my M1 Mac, but it is annoying. The weird thing is that sometimes it stops by itself... and then restarts. Ejecting external drive has no impact. Anybody has a durable solution for this? I've seen threads about this on at least three different macOS iterations so it's not only Big Sur.
Unfortunately, I had to reinstall Mac OS for this to go away. :/ Sorry. I've moved onto an M1 MBP and haven't seen it since.
 

Manuphoto

macrumors newbie
Apr 4, 2020
11
19
Montreal, Canada
Unfortunately, I had to reinstall Mac OS for this to go away. :/ Sorry. I've moved onto an M1 MBP and haven't seen it since.
Yeah, well I'll see. As I said, it often stops by itself and then comes back. It's not hindering the computer as far as I can tell, but I don't like having unchecked process running around. Maybe the next macOS update will fix that ?‍♂️. Thanks though.
 
  • Like
Reactions: BigMcGuire

iluvcrap2000

macrumors member
Jul 31, 2022
32
-5
I have a crap ton of images and the thumbnailer keeps accessing files. I have to keep killing it in activity monitor or else it''s hog cpu time and the fans goes on.one thing I tried is go to finder-view options then to icon previews and uncheck it, so quicklook won't show preview icons in the finder. the old way of having the icons already stored is much faster than having it constantly accessed. Apple's "Smart" Engineers aren't so smart. Sometimes the old way works fine and shouldn't be ****ed with.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.