Container and codec are different
MP4, MOV, WebM and MKV are containers. H.264/AVC, VP9, AV1, AAC and Opus are codecs carried inside them. Good conversion decisions account for both.
Prefer transmuxing when possible
If the existing tracks are legal in the target container, a conversion can sometimes copy encoded packets without re-encoding. That is faster and avoids generation loss.
Transcode only when compatibility requires it
When the target cannot carry the current codec, the browser must decode and encode the track. Browser codec availability is checked at runtime.
Use MP4 for broad delivery, WebM for web-native workflows
MP4 with AVC/AAC remains broadly compatible. WebM is useful for VP8/VP9/AV1 and Opus workflows. Choose based on the actual destination rather than file size alone.
Official marketplace references
Requirements can change. Review the source before publishing an important listing.
Mediabunny browser media toolkit documentation ↗