WebM with VP9 video and Opus sound is an open format that browsers play natively, which makes it a good choice for videos on websites. Converting an MP4 re-encodes the H.264 or H.265 video to VP9 and the AAC sound to Opus.
How to convert MP4 to WebM
- Upload the MP4 (or MOV, MKV and other videos; up to 2 GB).
- Choose Convert to: WebM and a quality: Balanced for most uses, High for more detail, Small file to save bandwidth.
- Download the WebM.
What you get
- Video: VP9, at the original size and frame rate (60 fps at most). Videos that are already VP8, VP9 or AV1 are copied into the WebM unchanged.
- Sound: Opus. Opus and Vorbis sound is copied.
- Subtitles: text subtitles are kept as WebVTT.
- Maximum resolution under “More options” makes a smaller file for web pages, for example 720p.
Using it on a web page
<video controls width="640">
<source src="video.webm" type="video/webm">
<source src="video.mp4" type="video/mp4">
</video>
Listing an MP4 as the second source covers browsers and devices that don't play WebM.
Things to know
- VP9 takes longer to encode than H.264. Short and medium videos get the more efficient encoder settings; long ones a faster setting, which makes somewhat larger files.
- Re-encoding is limited to about 25 minutes of 1080p video per file, and longer for smaller videos. For long videos, choose a lower maximum resolution.
- Upright phone videos are turned upright in the WebM.
More about what this tool reads and writes: Video Converter.