Safari is slow after Mojave update

I had the same problem as you mentioned and it turned out to be the Adblocker Pro extension. Perhaps you're also using an adblocker extension (uBlock?) and that might be the cause. Now I have to look for another Adblocker 😟

This may not be strictly relevant to the OP, but for others who say that sites containing a lot of graphics are slow (like iCloud with its cursor-tracking dynamic background): there appears to be some issue with Safari on Mojave not engaging high-performance graphics. Trying to draw complex stuff without using the GPU gets us this chunky 1990s-feeling performance and seems to back up the main thread so the whole computer bogs down.

For a battery-eating workaround you can turn off automatic graphics switching:
iCloud suddenly roars back to life - this de-***** the iCloud home page in real time - but you may lose battery performance if you have to leave this setting this way. Toggle it back off to return to late-nineties mode.

There were changes in Mojave to enable the use of external GPUs, and it's likely Safari didn't track them properly and now can't demand GPU on its own when it needs it.

Safari/Preferences/Advanced - enable the Develop menu, then go there and Empty Caches. Quit/reopen Safari and test. Then try Safari/History/Show History and delete all history items. Quit/reopen Safari and test. You can also try try Safari/Clear History…. The down side is it clears all cookies. Doing this may cause some sites to no longer recognize your computer as one that has visited the web site. Go to Finder and select your user/home folder. With that Finder window as the front window, either select Finder/View/Show View options or go command - J. When the View options opens, check ’Show Library Folder’. That should make your user library folder visible in your user/home folder. Select Library/Caches/com.apple.Safari/Cache.db and move it to the trash.

Go to Safari Preferences/Extensions and turn all extensions off. Test. If okay, turn the extensions on one by one until you figure out what extension is causing the problem.

Safari Corruption See post by Linc Davis

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Dear Apple,

let me ask you, what did you do with Safari? Since the Mojave released, the Safari is very slow, laggy, slow graphics, slow scrolling. Two-finger zooming is very slow also. In the meantime the Chrome is running smoothly, fast and responsive. If you need more information or any log file, please let me know, and please check the connected thread in your community forum. Pleeease.

https://discussions.apple.com/thread/8558341

And, in case you release a new version of MacOS, please add this version to this feedback form, beacuse I already updated the system to 10.14.3 and I can't select the correct version here. Perfect.

Guys, go to feedback site, and write something similar please. Thx.

Feedback - Safari - Apple

I have the same issue in YouTube and also it hangs when I try search within youtube.

I've tried all the above troubleshooting but nothing changed and I still have the same problem.

I believe Apple should intervene in this issue.

I have the same issue. Some web sites seem to work ok, but others, like amazon, are unusable. I thought maybe my laptop was too old for Mojave (I'm using a 2015 Macbook Air), but Chrome is flying. I've basically had to switch to Chrome as well. Safari is mostly unusable now

I've seen this as well. I finally broke down and came here to see if it was common or not...and it apparently is.

The worst offender is, ironically, icloud.com. The site is completely unusable in safari now. The framerate for that site's animations, rendering, reactivity, etc, seems to be hovering around 1 frame every 2-5 seconds or less... Naturally it works fine on Chrome.

Apple needs to just replace the safari's with the open source chrome one if they're not going to actually put effort into developing it. Safari is all-but bloatware now.

I'm running 1Blocker from the App Store right now. Performance is fine, not slowing down whatsoever - however a bit aggresive but the 'Reload without content blockers' option in Safari is not far away when needed.

Don't know. All I do know is that I tried everything else first. After all that I still had the problem so I looked for anything which was out-of-date. Only Java was not the current version. After updating, all was well! Whatever the root cause was, I'm monitoring the situation incase it all falls down around me.

Me too especially in Facebook, Twitter, or any website with lots of graphics or pics and in You Tube as well, or when I try to download a GIF, JPG, any photo or emoji. Reminds me of WINDOWS XP which was crap that's why I switched to MAC. I noticed no issues with Chrome or Firefox but I got used Safari that I don't like to switch browsers since I have all my bookmarks saved and some of them wouldn't transfer over to either one so I stuck with Safari. I do notice that my memory gauge states I go from 28% which is always normal for my MacBook Retina Pro to 58-65% used when I open Safari. I cleaned out every cache possible, history, ran memory clean rebooted several times, and the memory goes back to 28%. As soon as I open Safari, up it goes like high blood pressure! 😝 Perhaps the developers should have a go and fix this Mojave issue or else a lot of Safari users will be jumping ship and finding other browsers.

I was having a similar problem--I could be, say, in my amazon cart and nothing, no clicks or mouse movement would register for at least an extra 5 or 10 seconds. youtube, forget about it. And google docs just froze instantly.

I turned off all my extensions: ad blocker and honey, I think it worked but I need more time to confirm 100%.

MPB 2016 15" i7 16GB RAM. Mojave.

Same here. Safari 12 on Mojave is virtually unusable for me, loads pages very slowly, regularly just stalls and generally has a detrimental effect on the whole system. A good example is YouTube which stutters and runs terribly. Moved across to Chrome and all is well so until this is addressed by Apple I'll be using that.

My Macbook 13" 2015 has the same problem. Sometimes the Safari stay everything black and stopped the computer.

I don't have any problems with others Browsers, I was waiting for an Update and until today has nothing.