Short answer
MP4 plays essentially everywhere and is the right default for sharing, uploading or sending a file to someone. WebM is royalty-free and well suited to web pages, but it cannot carry every codec — notably AAC audio — which is the usual reason a converted WebM ends up silent.
MP4 vs WebM, side by side
| Aspect | MP4 | WebM |
|---|---|---|
| Device compatibility | Universal | Browsers yes; many devices no |
| Video codecs carried | H.264, H.265, AV1 | VP8, VP9, AV1 |
| Audio codecs carried | AAC, MP3, ALAC | Opus, Vorbis only |
| Licensing | Patent-encumbered | Royalty-free |
| Streaming support | Excellent, widely tooled | Good in browsers |
| Typical file size | Depends on codec, not container | Depends on codec, not container |
A container is not a codec
MP4 and WebM are containers: they hold compressed video, audio, subtitles and metadata together in one file. They do not themselves compress anything. The codec inside is what determines quality and file size.
This is why "MP4 is better quality than WebM" is not a meaningful statement. The same H.264 video stream in either container is bit-for-bit the same video. What differs is which codecs each container is allowed to hold, and what will play it.
The silent-audio trap
WebM accepts only Opus and Vorbis audio. MP4 files almost always carry AAC. Convert an MP4 to WebM while copying the audio stream instead of re-encoding it, and the audio is either rejected or written in a way nothing will play — producing a video with no sound.
The fix is to re-encode the audio to Opus rather than copy it. Our video tools do this automatically when the target container requires it, which is why a converted WebM from here keeps its sound.
Frequently Asked Questions
Which has better quality, MP4 or WebM?
Neither — quality comes from the codec inside, not the container. The same video encoded at the same settings looks identical in both. Choose the container based on what needs to play the file.
Why does my WebM have no sound?
The audio was almost certainly copied from an MP4 as AAC, which WebM cannot carry. Re-encode the audio to Opus instead of copying the stream.
Can I upload WebM to YouTube or Instagram?
YouTube accepts WebM. Many other platforms only accept MP4, and some accept it nominally but re-encode it badly. MP4 with H.264 and AAC is the safe upload format.
Try it yourself
Terms used here
Related comparisons
- H.264 vs H.265 vs VP9 — H.264 unless you have a specific reason. H.265 or VP9 when file size matters more than compatibility.