MP4 or MKV: which file should you choose?

Understand containers, codecs and the Fetchoo profile intended for phone compatibility.

1. MP4 and MKV are containers holding video and any audio present in the source. Renaming .mkv to .mp4 does not convert the contents.
2. After inspecting a link, select H.264 MP4. This profile converts video to H.264 and existing audio to AAC. The 720p profile produces a smaller file; 1080p preserves more detail when the source provides it.
3. HEVC is a separate option for compatible devices. It can reduce file size, but older players support it less consistently. Original format follows the source and may be MKV or WebM.
4. Save the completed file and open it in your player. If the player rejects it, process it again as H.264 MP4 rather than manually changing the extension.

Fetchoo checks include full MP4 decoding, H.264, AAC and fast-start metadata. They do not represent testing on every phone model.

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Reviewed October 23, 2026. Only use material you have permission to process.