What you should know
MP4 (MPEG-4 Part 14) is a video container standardised in 2001. It compresses nothing itself: it wraps a video track — usually H.264 or HEVC —, one or more AAC audio tracks, and optionally subtitles and chapter metadata.
It is the format devices, browsers, TVs and sharing platforms read most readily. A well-encoded MP4 opens almost anywhere without extra software, which is why it is the default target for most video conversions.
Strengths
- Read by virtually every player, phone, browser and sharing service
- Good balance between image quality and file size
- Streaming works as soon as metadata sits at the front (faststart)
- Holds several audio tracks and subtitles in a single file
Limitations to know
- The container does not dictate a codec: an MP4 may hold an exotic encoding some players refuse
- HEVC, although very efficient, is not read by every desktop browser
- Converting to MP4 almost always means re-encoding, so quality drops if the bitrate is chosen poorly
- Long files quickly exceed the memory available to a browser tab during on-device conversion
When to use it
Pick MP4 to share a video, publish it on the web or play it on a device whose capabilities you do not know. If you are merely renaming an H.264 MOV without touching the settings, the conversion happens without re-encoding: the gain is immediate and the quality strictly identical.
Quality, size and compatibility
Final quality depends on the codec and bitrate, not the extension. At a given resolution, too low a bitrate produces blocks in fast motion; too high inflates the file with no visible gain. For video already encoded in H.264 inside another container, prefer remuxing: no extra generation loss is added.
Frequently asked questions
- MP4 vs MOV: what is the difference?
- Both belong to the MPEG-4 family. MOV is Apple's historical container, MP4 a more universal standardisation. An H.264 MOV often becomes MP4 without re-encoding, and therefore without loss.
- Why is my converted file larger?
- Re-encoding at a higher bitrate than the source inflates the file without improving the image. Start from the original quality, or pick a size-reduction setting if weight matters.
- Is MP4 a free format?
- The container is publicly specified, but the codecs it most often carries, H.264 and HEVC, are patent-encumbered. That does not prevent using it, including with free encoders such as x264.