my videos were playing fine from iphone to mac until the last few hours, how they wont play and suddenly say I need quicktime

Hi delia73,

Thanks for coming to Apple Support Communities for help today playing iPhone created videos on your Mac. It sounds like you now are required to have Quicktime to play them.

It's difficult to know why this requirement was suddenly specified, but it could be due to the file format.

The good news is, Quicktime is part of macOS. You can find it in your Applications folder. You can also read more about it here: QuickTime Player Support.

Also, please read this page on compatibility: About QuickTime 7 compatibility.

Have a fantastic day!