I have used Firefox on a 27" MAC for many many years. In fact I have used Firefox on many macs since Firefox was first offered. As of the last update or browser upgrade offered by Mozilla for Firefox for Apple desktops, most all streaming video service no longer work. YouTube, Amazon Prime, and Netflix all stall after a minute or less of selecting a video from the above vendors. I get the little spinning arrow, and then a screen message that states that my ISP is not providing me with enough bandwidth to stream video. Absolute nonsense. Using Safari I have absolutely no issues, problems, stalls, buffering, error messages etc., and the experience is what I used to get from Firefox. I have lots of bandwidth available, and have had a professional network engineering service provider check my internet connection. Even if I make sure no other tabs, applications or other iterations are running, ONLY Firefox, it stalls and will not play video. Then I get another screen message that states that "maybe if you restart your device you may be able to play video". While I realize that Firefox is free, I still think I should have a reasonable expectation that it will continue to provide buffer, stall, and hang free performance when I want to watch YouTube, Amazon Prime and or Netflix.