I recorded a video with my iPhone and it won’t play. Says format not supported.

katarina221,

Are these videos being recorded in the standard video mode or another mode such as Slo-Mo?

If you haven't already, please restart your iPhone and the Photos app. This will refresh everything and can fix many issues. Also, if your iPhone is not already updated to the latest software version, we recommend updating as outdated software can cause things to misbehave. You can update following these steps:

1. "Back up your device using iCloud or your computer.
2. Plug your device into power and connect to the internet with Wi-Fi.
3. Go to Settings > General, then tap Software Update.
4. If you see two software update options available, choose the one that you want to install.
5. 
6. Tap Install Now. If you see Download and Install instead, tap it to download the update, enter your passcode, then tap Install Now. If you don't know your passcode, learn what to do."

These steps and more tips for updating can be found here: Update your iPhone, iPad, or iPod touch.

Hope that helps!

Thanks for getting back to us here in Communities.

Do you recall if these videos were recorded with the Camera app or using a third party app?

The videos that aren't working, were they recently taken or are they older videos?

Additionally do you have any other devices that you can send the videos to and see if the same thing occurs with the playback?

Are you using iCloud Photos? If so, try logging into iCloud using a web browser and see if the video plays there with no issue.

These steps may help us narrow down the issue.

Cheers!

Greetings katarina221,

Where exactly are you attempting to play this video? Does this happen with all recorded videos, or only one?

Play videos and slideshows in the Photos app on iPhone - Apple Support

Take care.