Make sure you are not blocking content.

Start Firefox in Safe Mode {web link} by holding down the <Shift> (Mac=Options) key, and then starting Firefox.

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

Thank you, FredMcD. I did as you suggested and there was a slight improvement when playing in safe mode, in that there was still a lot of buffering before it started to play. But then the video would, stop, play, stop, play, etc.

I also checked the status of flash player and it appears to be up to date.

What kind of issues do you have playing media files?

You can check the Web Console for media related messages if there are problems on a website.

• "3-bar" menu button or Tools -> Web Developer
• https://developer.mozilla.org/en/Tools/Web_Console

This happens on every website I've gone to that had a video.

The video is black. A whites circle in the middle of where the video should be just spins like its buffering. In regular mode, the video never starts. In safe mode, it buffers for about 10-20 seconds, then starts, stops, starts, stops, etc. I've cleared cache/cookies. I've shut down and restarted the mac.

i.e. when I try to navigate sites like facebook, I get a multi-colored wheel that just spins and spins. (Even when the wheel finally stops spinning, facebook no longer functions properly in firefox.) This happens on websites I've been using for years with firefox. Websites haven't functioned as well in Firefox as they do in safari for a long time now.

BUT the reasons I still try to use firefox are because it allows me better cookie control than safari does and there's no add-on like lazarus for firefox or safari.

I was hoping that someone could tell me if updating to 52.6 would help. It seems that every time I update firefox, something that used to work doesn't. And it just keeps getting slower and slower.

Here's what was in the web console. I have no clue what it means.

         Font-Check :: Error while reading from sessionStorage DOMException [SecurityError: "The operation is insecure."

code: 18 nsresult: 0x80530012 location: https://cdn.mdn.mozilla.net/static/build/js/font-check.713e9d01025c.js:1] font-check.713e9d01025c.js:1:489 Font-Check :: Error while reading from sessionStorage DOMException [SecurityError: "The operation is insecure." code: 18 nsresult: 0x80530012 location: https://cdn.mdn.mozilla.net/static/build/js/font-check.713e9d01025c.js:1] font-check.713e9d01025c.js:1:489 SecurityError: The operation is insecure. main.226517b2a7dc.js:5 Fonts.js :: Error while reading from sessionStorage DOMException [SecurityError: "The operation is insecure." code: 18 nsresult: 0x80530012 location: https://cdn.mdn.mozilla.net/static/build/js/main.226517b2a7dc.js:5] main.226517b2a7dc.js:5:30932 Fonts.js :: Error while reading from sessionStorage DOMException [SecurityError: "The operation is insecure." code: 18 nsresult: 0x80530012 location: https://cdn.mdn.mozilla.net/static/build/js/main.226517b2a7dc.js:5]