MacOS Sonoma will not play MP4 files

I have to use VLC for Mac to open it. This is very critical as the format will be used forever.

To continue my last post. Too bad, Apple cannot higher employees that have the knowledge to solve problems.

I could say something derogatory like the previous employer of the Apple employee was McDonald's', but I understand that would be rude.

This is a user-to-user forum. Apple Support staff doesn’t participate here.

Did you have an issue yourself (if so, please describe), or are you just searching old forgotten posts to reply to with unsubstantiated complaints?

User gregeb gave the right answer for this thread.

Temporarily converting files using https://handbrake.fr/ but hope Apple will fix QuickTime in next iteration.

Here's one option: Safari!

Back story: the issue is VP9 video which Apple is not eagerly supporting. However it is now being supported for web videos on iOS and Mac. But only in a web context, not files.

Drag the file into the address bar on Safari.

In Chrome, drag and drop the file on the browser window.

In Opera, select File > Open File.

It's inelegant, but it works. VLC also works for me, but I watch talking heads at 2x speed and VLC can't cope with VP9 at that speed - at least not on elder Mac. Having checked, it seems fine on Mac Studio

Sonoma doesn't allow to install this app