Video formats explained: MP4, MKV, H.264 and HEVC in plain English

When a video will not play, the cause is usually the format. Two ideas explain most of it.

Container

The container is the file wrapper, shown by the extension: MP4, MKV, MOV, WebM. It holds video, audio, subtitles and metadata.

Codec

The codec compresses the video. Common ones:

• H.264 (AVC): widely supported, a safe default.
• HEVC (H.265): smaller files at similar quality, but support varies.
• VP9 and AV1: modern, efficient, used by streaming services.

A player needs both the container and the codec to work.

Resolution and bitrate

• Resolution: 720p, 1080p, 4K. More pixels, more detail, bigger files.
• Bitrate: how much data per second. A low bitrate at high resolution still looks blocky.
• Frame rate: 24, 30, 60 frames a second. Higher is smoother and larger.

If a file will not play

1. Try a different video player that supports more codecs.
2. Update the app or the phone.
3. Convert the file to MP4 with H.264 if it came from your own recording.

Only convert or save content you have the right to use. See downloading videos legally and freeing storage.