Safari keeps crashing/freezing after install of El Capitan

I was in the exact same boat as you.

And I have almost the same model as you I think:
iMac 5K Retina (late 2015)

4GHz i7

32 GB RAM

AMD Radeon R9 M395X 4096 MB

Since April It started the same issues you're having, around the same time I updated to OSX 10.11.4

After months of taking my iMac to the Apple store and my reseller, talking with them to find a solution.
I finally got my logic board replaced, it's been 3 days and still no crashes or reboots... (knocks on all the wood).

I did have to get real firm with people at Apple and my reseller.
They treat you like a **** thief so be prepared for that.

For everyone else with similar problems, I pretty sure this is not software related anymore.
This has to be hardware related.

Good luck,

Nick

Hi Nick. Not sure if you got my reply, which I thought I had sent! I did think that an update would solve the problem, but in fact the 10.11.5 update seems to have exacerbated the problem. I really didn't want to go down the route of taking it into an apple store, A- because there isn't one near me and B because from what I have read on this site, they haven't been able to solve the problem - even replacing the logic board! My brother has recently bought the same iMac and has had no problems whatsoever - possibly because it has slightly different hardware, so it seems that it is incompatible hardware that the update has interfered with. Thanks for your advice, and I will report back.

I have a similar issue. Mid-2014 MBP base model no dGPU.
Usually for the first few hours of youtube browsing and watching videos etc. Nothing significant really happens. Then out of nowhere safari starts lagging up BAD!. also freezes happen when closing a tab? Then, if I continue watching a video or start watching a new video, it freezes my entire mac completely! I have to wait it out for half a minute before my mac becomes somewhat responsive again. However, from this stage, safari is on a freeze-unfreeze cycle. Not to mention web pages have some sort of loading cycle.. Like it would load the youtube homepage half way, then half a minute later it would load the rest of youtube homepage. Similarly with other websites. If I want to stop the freezing, I have to restart my mac. Force quitting and starting up safari anew does not fix anything...

Can confirm sporadic freezes in Safari when closing tabs with HTML5 video, namely YouTube. Remains unresponsive for 60-180 seconds, then lags and stutters until restarted. Clean installs, dirty installs, betas, releases – doesn't matter, it's there.

OSX 10.11.5, rMBP15 Mid 2014, Iris Pro, Wipr content blocker, no Flash.

Has been this way since the Yosemite days. Really annoying.

I should have read the thread before replying. Exactly my situation. Exact same MBP. Exact same extension and no flash too!

I can offer my two cents solution: when Safari gets slower, try to clear History using Option key in order to Keep Web Data intact.

As stated in countless threads, this isn't a history or cache problem. Safari works perfectly fine until you either close a tab that had video playback, or you start playing a video etc. After you do so, the entire mac freezes up for half a minute or so, and then repeats and becomes worse if you keep navigating safari. Everyone here already tried straight forward things like disabling everything, clearing everything, restarting everything, reinstalling everything.. It only gets resolved with a reboot until it happens again.

Just noting that Safari Technology Preview 8 doesn't do anything to solve the crashes.

More time wasted.

With regard to the "Remove All Website Data" suggestions...I've noticed that Twitter just constantly repopulates, even if I delete turn off WiFi, delete Twitter cookies, and turn of Twitter in my Internet Accounts prefs panel.

This is just to confirm that 10.11.6 released yesterday does not fix the issue, which was of course to be expected.

Updated to 10.1.6 with no visible improvement in browsing and speed.

Now, the promise of Sierra is a new hope, but not for MacBookPro 2009 users as myself.

So, this is 'thank you' for my 28 years of loyalty to Apple?

I guess people with discrete GPU don't have the issue, so maybe Intel integrated GPU is cause of all this. Although I didn't have any problems with Yosemite...

It seems that the issue may have been fixed with 10.11.6! I'm not exactly sure, but apart from one freeze that happened a while ago which may not be related, I have not noticed much freezing after closing YouTube tabs at all lately. It used to happen multiple times a day, and that doesn't seem to be the case since this last OS X update.

Has anyone had these freezes since updating to 10.11.6? I'm only specifically talking about freezes after closing YouTube tabs in Safari, not anything else.

I have not seen this issue since the update either. I've tried to get it to occur without incidence. I also did some heavy work interacting with YouTube this week with no problems. I'm going to be working with YT in the next day as well. If there is an issue, I'll report back.

Apple is aware of the problem and the specifics. I suspect that they may be checking to see if 10.11.6 rectified the problem.

Anyone else?

Haven't had a freeze yet, as well. Although, I'm on STP.

Got approached by an Apple rep couple months ago about this issue (they were monitoring this thread). Scheduled a call in order to figure out what was causing this issue, but unfortunately I wasn't available when he called couple times. I guess he reached someone else from this thread and Apple finally fixed it (I hope).

And a week and a half later, how is 10.11.6 faring for those who had the tab close/switch freeze? I've made backups and am about to update to it later.

I haven't had any freezes since 10.11.6.

After more than a year, it's nice to have that additional productivity time back.