MP4 to WebM Converter

A video on your own website is delivered thousands of times, so every megabyte saved adds up. WebM's VP9 codec stores the same picture in fewer bytes than the H.264 codec most MP4 files use, which means faster starts and less bandwidth, especially for large hero videos and product loops.

The other reason is licensing. The WebM project FAQ states that Google does not demand royalties for the codecs WebM supports. That matters for open-source projects and for anyone who prefers to avoid patent-encumbered formats on their own platform.

WebM is a web format first. For sending a clip to someone, posting on social media or playing it on a TV, MP4 remains the more practical choice; the usual setup on a site is to offer both.

The converter writes VP9 video and Opus audio. Resolution and frame rate stay as they are unless you change them, so a 1080p MP4 becomes a 1080p WebM. Encoding VP9 takes longer than encoding H.264, so a long clip can take noticeably more time than an MP4 conversion of the same length.

Quality is set by the same scale used for every video conversion on the site, where lower numbers mean better quality and bigger files. The default is a sensible middle for web playback. For a hero video that sits behind text, you can go a step lower in quality without anyone noticing, because the picture is partly covered and constantly moving.

Google announced WebM in 2010 together with VP8 support in Chromium, and later added VP9 as a more efficient successor. Over the following decade every major browser engine added support, with Safari among the last. Today WebM plays in current Chrome, Edge, Firefox and Safari, which makes it a dependable second source for site video.

A newer codec, AV1, is also used in WebM files by some sites, and it compresses even better than VP9. It takes much longer to encode and older hardware decodes it slowly, so VP9 remains the practical choice for most websites today.

The browser tries the sources in order and plays the first one it can decode, so listing WebM first and MP4 second gives modern browsers the smaller file and everything else a working fallback. MDN's video element reference explains the attributes, including muted, loop and playsinline for background clips.

Give both files the same dimensions and the same poster image so the page layout does not jump, whichever source the browser picks. If you host video on a content delivery network, upload both files there and keep the file names parallel, for example intro.webm and intro.mp4, so they are easy to update together later.

Converting a whole library is a common job when a site is redesigned. Each MP4 becomes a WebM with the same name, so you can upload the new files beside the old ones and add the extra source line to each page.

Convert up to 20 MP4 files at once, each up to 95 MB. Uploads are removed after processing and the WebM files 30 minutes later. For a short silent loop, an animated format may also work: Video to GIF makes GIFs, although a muted WebM loop is usually far smaller. To go back from WebM to MP4, use WebM to MP4, and the Video Converter covers every other pairing.