If you are downloading a non-protected M4V from a website, most modern browsers will play the video in a tab rather than downloading it. To force a download, right-click the video link and select "Save Link As..." . Opening M4V Files

M4V is a video container format developed by Apple that is very similar to MP4 but often includes DRM copy protection . Because of these restrictions, downloading and playing "final" M4V files can sometimes be tricky outside of the Apple ecosystem.

If your device doesn't support M4V, you can convert it to the more universal format: What Are M4V Files? | M4V Format Explained - Adobe

Most M4V files are downloaded directly through iTunes or the Apple TV app. To download purchased content, ensure your computer is authorized with your Apple ID.

Use QuickTime Player or iTunes, which are the native applications for this format.

These files generally must be played within Apple’s authorized apps. Attempting to open them in third-party players like VLC will usually result in an error unless the DRM is removed. Converting M4V for Better Compatibility

If the file is unprotected , you can use the VLC media player , which is a free, cross-platform tool that supports most M4V streams.