Q: Why does Mac Safari stutter playing YouTube videos?

You're addressing other users here, not Apple.

When the video starts to play, stop it. Leave it stopped until the loading bar is at least halfway across, then start.

You posted in the correct forum...  Most YouTube content requires the Flash plugin. Try troubleshooting.

Quit Safari.

Open System Preferences > Flash Player then select the Storage tab. Click: Delete All

Now uninstall the Flash plugin then reinstall new >  Troubleshoot Flash Player | Mac OS'

Very important to uninstall the currently installed Flash plugin first before reinstalling.

Launch Safari From your Safari menu bar click Safari > Empty Cache

Now try a video.

BTW... if you have the ClickToFlash extension installed, that can prevent Flash based video from streaming. It can also be installed as a plugin in /Library/Internet-Plug-Ins.

And check to see if Safari is running in 32 bit mode. Right or control click the Safari icon in your Applications folder then click Get Info. If the box next to:  Open in 32 bit mode  is selected, deselect, quit then relaunch Safari.

BTW, this is not an Apple issue. Flash is third party software for which Apple is not responsible for developing or updating. That's Adobe's job.

Thoughts on Flash

Thank you Carolyn.  I was bedeviled by this problem and searched long and hard to find a solution.  At first, I searched for Mac>Safari>stutter and didn't find much.  When I changed the search to YouTube>Stutter I came across your post here.  The stuttering SEEMS to be gone now, but I won't be comfortable until I get a couple of days of experience.

I remember well that statement from SJ 2+ years ago.  It's unfortunate that migration from Flash to HTML5 hasn't been more rapid.  In addition to following your very clear and helpful instructions re Flash, I now have ClickToFlash activated. 

Many thanks.

Bob Kelly

I too thank you Carolyn.  Your steps have solved my stuttering problems!

I followed Caroline's instructions and it didn't seem to fix it.  With this clip:

http://www.youtube.com/watch?v=9p0BqUcQ7i0&list=UUmKurapML4BF9Bjtj4RbvXw&index=3

I was getting around 150 dropped frames in Safari and none at all in Chrome (both browsers playing the same 1080p flash clip, not HTML5).

But after a reboot, Safari now seems fixed.  I notice Safari downloads the whole clip straight away now, wheres before it did not - it downloaded it little by little. I have an 80MBit internet connection (76Mbit actual) so buffering should not cause stuttering, but it clearly was doing.

Strangely, when playing the same clip in Chrome, it does not download the whole clip straight off, just a bit at a time - but still no stuttering.

There is clearly something wrong with either the Flash Plugin, or Safari or a combination of the two.

Hmmmm.  I spoke too soon.  It has not fixed it.

For some reason, *sometimes* in Safari flashplayer will download the whole movie straightaway all in one go.  In that case, it doesn't seem to stutter.  But on other occassions, it only downloads the movie a piece at a time, as it is playing.  Then it drops lots of frames.  200+ dropped frames playing the clip above just now.

Chrome and Firefox play the same clip flawlessly :-(

Incidentally, I tried a complete reset of Safari back to system defaults.  Removed all plugins, resinstalled flashplayer (again), reinstalled JAVA.  No difference... still broken.

I'm having the same problem, but only in the last week or so. I'm wondering if it’s the version of the Flash Plugin.

I'm still on OSX 10.7.5, with Safari 6.1.

I'll try an update to Mavericks later this week.

Don't see anything else on this thread since March?

For me, some flash videos sutter in firefox & safari but chrome plays them fine. youtube works fine in all browser. strange. i think its the way flash handles videos on mac. Chrome has their own built-in flash player where as firefox and safari will use the plugin that user installs. So google may have tweaked and ironed out more issues in their version of flash.

Can anyone help me out in this?

I believe this link here will solve stuttering video problems in Youtube and etc. It fixed my video problems.

http://www.idownloadblog.com/2014/04/18/how-to-fix-choppy-video-playback-in-safa ri-on-os-x/