WebM is an open-source, royalty-free video container format developed by Google for web video. It was designed to provide an open alternative to MP4 with H.264 (which has patent licensing costs). WebM typically uses VP8, VP9, or AV1 video codecs with Vorbis or Opus audio. All major browsers support WebM natively.
WebM with VP9 offers similar compression to H.264 MP4, while WebM with AV1 achieves significantly better compression — up to 50% smaller than H.264 at the same quality. Google uses WebM extensively on YouTube. However, MP4 remains more universally compatible, particularly for downloads and non-browser playback.
Choose WebM for web video elements where you control playback in a browser, particularly if using AV1 for maximum compression. Choose MP4 for downloads, sharing via messaging apps, or any situation where the viewer might use a non-browser player. FileCurve's video tools work with WebM input files.