Many site issues can be caused by corrupt cookies or cache.

• Clear the Cache and
• Remove Cookies

Warning ! ! This will log you out of sites you're logged in to. You may also lose any settings for that website.

• Cookies; Delete cookies to remove the information websites have stored on your computer {web link}

• Cache; How to clear the Firefox cache {web link}

If there is still a problem, 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). Did this help?

While you are in safe mode;

Try disabling graphics hardware acceleration in Firefox. Since this feature was added to Firefox it has gradually improved but there are still a few glitches.

How to disable Hardware Acceleration {web link}

i have the issue with a fresh install too, maybe it's an hardware accelleration issue, but my cpu hit hard without hw acccelaration, video + gaming. isn't a solution but a workaround. i prefer stay with another browser instead disable hw acceleration. Thank you for answering anyway.

My rig: i5 4670 1060 6gb 16gb ram

Did you change your hardware acceleration settings in FF to see what happens.

I have the exact same issue as in the video, and for some reason it only started popping up recently, on my old rig as well as my new one.

My new rig is a i5 8600K, 16Gb DDR4 and a 1060 6Gb, so it should definitely be able to handle whatever Firefox can throw at it, yet I've read about fairly many people having this exact same issue, and nothing has been done to try and find the bug. Because it is a bug.

Disabling hardware acceleration causes videos to lose quality. Dark scenes become stripey, and that's not something you should just 'accept'.

Mozilla, please fix. I hate Chrome slightly more than Firefox with this bug.

I called for more help.