I suggest updating all video and sound drivers.

Since it is a Beta they have recommended using only Safari

Am thinking this is possibly not a Firefox issues as per above.

Possibly google issues for this OS and all so google for their beta support page to see if others are having issues or they have found issues in video/sound.

Please let us know if this solved your issue or if need further assistance.

There is no issue with video and sound drivers in macOS High Sierra, the same video plays nicely in Safari with the same computer and the same OS.

It is a Firefox issue, the online streaming for some games (soccer, baseball, ESPN) flickers constantly in Firefox, sometimes does not play at all, Youtube videos don't have sound at all. Same web sites stream nicely in Safari with no issues whatsoever.

Firefox had no problems playing these videos before with a stable macOS Sierra, the issues came around with the new macOS High Sierra Beta, and you are right, since this OS is a beta I will use Safari in the meantime. Hopefully, Firefox engineers can catch up with the new system before Mac delivers the final version of High Sierra.

> It is a Firefox issue, the online streaming for some games (soccer, baseball, ESPN) flickers constantly in Firefox, sometimes does not play at all, Youtube videos don't have sound at all. Same web sites stream nicely in Safari with no issues whatsoever.

Since you're using a Beta macOS, it's expected that some things won't work in Firefox as they do in stable macOS. I'm curious on how Nightly will perform though. Do you mind giving that a try?

> Hopefully, Firefox engineers can catch up with the new system before Mac delivers the final version of High Sierra.

I wouldn't worry too much.

I understand some things are not going to work as usual with a Beta OS, it is normal. I am a Firefox user, has been for almost 10 years, even with my previous Windows computer. Since I changed to Mac, it has been my default browser and I love it, it has everything I need and more.

That being said, I am not worried, I know you guys are going to work out the inconsistencies with the new macOS and come out with an outstanding new browser by the time Mac delivers the upgraded OS.

I downloaded the Nightly version, very nice and very solid, I didn't know there was such a beta program on the works with Mozilla, I will keep a closer eye on you guys. I tried Nightly with the websites that have been having issues with Firefox and I got the same problems: Youtube videos with no audio and the sports websites with flickering-inconsistent video.

I will keep testing Nightly, I like it.