Safari has been stalling when I load some websites. Github.com is the most reproducible. The page would load, but then my mouse would turn to a beach-ball and just get stuck until I close the tab with Github or whatever site seems to be causing it.

I am not running any extensions - to be honest I don't know what it could be. My boss is having the same issue as well. I have no issues with loading Github on Chrome.

I am running macOS Sierra (10.12.1) on a Late 2014 Mac mini and Safari 10.0.1. It also happens on the Safari Technology Preview (Release 26, 10.2)

What are ways to fix this or further diagnose slow web sites in safari?

  • I'm on 10.1, but I do remember having similar symptoms a few months back (may have been a previous version of Safari) and it was something wrong with https certificates
    – dwightk
    Apr 1 '17 at 17:03

Release 26 of Safari TP contains many changes to the rendering engine. This causes problems with many websites, especially where image sprites are used extensively.

This will likely be fixed in the next release, but until then, you can just use the standard install of Safari, or downgrade to the previous version of Safari TP if you still have the installer. You can also try running with Disable Caches selected in the Develop menu.

  • I don't have any issues with Version 10.1 (12603. and newer on GitHub or the other web sites I use. I do use the ghostery extension to block most javascript trackers, so you might try that? Github is really clean though in terms of site design - so ghostery can help a lot on more advertising based sites. Not sure it's worth the install if GitHub is your issue.
    – bmike
    Apr 1 '17 at 16:55

Safari's web inspector is where I'd start. Use the develop mode in settings and then navigate to https://github.com and turn on the Timelines view.

enter image description here

After a few refreshes, you should have the home page cached and rendering in less than 2 seconds.

Then try a project page (which should render much faster than your home page or the main home page).

That renders for me in 400 ms or so repeatably with some longer running events that don't affect the initial page load to my eyes.

project page

If you think there are network delays (or SSL negotiation / checking issues) the network view will show your Safari stalling or not requesting resources in a timely manner. Check performance against another network if you can - web filtering or proxies can cause what you're seeing. Hard to know without some more details.

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