WebM is the open video format of the web: VP8, VP9 or AV1 video with Opus or Vorbis sound. Many video editors, phones and messaging apps still expect MP4 with H.264. Converting WebM to MP4 re-encodes both streams into those formats.
How to convert WebM to MP4
- Upload the WebM file (up to 2 GB).
- Keep Convert to: MP4 and choose a quality: Balanced looks like the original, High keeps fine detail in a larger file, Small file saves space.
- Download the MP4.
What changes
- Video: VP8, VP9 and AV1 are re-encoded to H.264. MP4 can technically hold VP9 and AV1, but many players don't play them from an MP4, so H.264 is the safe choice.
- Sound: Opus and Vorbis are re-encoded to AAC. Every sound track is kept.
- Subtitles: WebVTT subtitles become MP4 text subtitles.
The picture keeps its size and frame rate. Screen recordings and web downloads sometimes have odd sizes; the MP4 is rounded to even dimensions (a codec requirement), which changes the size by at most one pixel.
Tips
- Transparent WebM (VP9 with an alpha channel) becomes an MP4 without transparency, because MP4 with H.264 can't store it.
- Long recordings: re-encoding is limited to about 25 minutes of 1080p video per file (more at lower resolutions). For longer recordings, choose a lower maximum resolution under “More options”, or cut the recording into parts first.
- To go the other way, see MP4 to WebM.
More about what this tool reads and writes: Video Converter.