MP4
MP4 is a container, not a codec. It often wraps H.264 or H.265 video and AAC audio. The file extension does not tell you the codec.
Common uses
- Web video
- Phone recordings
- Social uploads
Strengths
- Universal playback
- Streaming-friendly
- Metadata boxes
Weaknesses
- Codec licensing around some payloads
- Variable browser decode for HEVC
Compatibility. H.264/AAC is the web’s safest pair. HEVC in MP4 is not safe everywhere.
Size and quality. Depends entirely on codec and bitrate, not on the letters MP4.
How to open it. Any modern player. Use the video inspector for duration and size.
How to convert it. The video compressor re-encodes a short clip in this browser to H.264 MP4 or WebM, with an 80 MB and 90-second cap. Longer files still belong in an editor.
Security and privacy. Media files are untrusted binaries. Metadata can include location. ConvertPass does not execute streams.
Related tools
- Video compressor
Auto-compress a short clip locally to MP4 or WebM, using this browser’s encoder.
- Video file inspector
Read duration and resolution from a video without uploading it.
- Video bitrate calculator
Turn file size and duration into an estimated bitrate, locally.
Related comparisons
Last reviewed 16 August 2026.