MP4 to WebM Converter

WebM is the open video format made for the web: every current browser plays it, and many websites use it for background and product videos. This converter turns MP4 (and MOV) files into WebM with VP8 video and Vorbis sound, in your browser with the ffmpeg engine (about 30 MB, downloaded the first time). Choose a quality level, cap the resolution, and remove the sound for a silent autoplay background. Your files are never uploaded.

How to use this tool

1. Choose the quality level and, if you like, a maximum resolution.
2. Tick "Remove the sound" for a website background video.
3. Choose one or more MP4 files; conversion starts right away.
4. Play the WebM in the page and download it.

Formula

File size ≈ average bitrate × length ÷ 8 (the bitrate stays under the level's cap)

Video is encoded with libvpx (VP8) in constant-quality mode with a bitrate ceiling: 5, 2.5 or 1 Mbit/s. Sound is Vorbis at about 160 kbit/s (about 112 at "Small"). Files that are already VP8, VP9 or AV1 with Opus or Vorbis sound are repackaged without re-encoding. VP9 and Opus are not offered because the in-browser engine cannot encode them reliably; VP8 plays everywhere WebM does.

Example

A 30-second 1080p hero video at the Standard level stays under 2.5 Mbit/s: at most 2.5 × 30 ÷ 8 ≈ 9.4 MB, usually less for calm footage. Capped at 720p with the sound removed, it typically lands around 4–6 MB.

How long it takes

VP8 encoding in the browser runs on one processor core: roughly 50 frames per second at 360p and about 7 at 1080p on a recent computer, so a 30-second 1080p clip at 30 fps takes about two minutes. Capping the resolution at 720p roughly doubles the speed.