Free MP4 to WebM converter

How do I convert MP4 to WebM?

Add the MP4 above, keep WebM as the output and click convert. The video is re-encoded to VP9 (or VP8 where your browser has no VP9 encoder) and the sound to Opus, on your own device. You download a .webm file ready for the web.

When should you use WebM?

WebM is an open, royalty-free video format made for the web. Every current browser plays it, and it’s the format of choice for many open-source projects and web platforms. Use it when:

• A website, CMS or web app asks for WebM uploads.
• You self-host video on a web page and want an open format next to MP4.
• You build a web app that plays short clips, such as onboarding animations or product tours, and want an efficient codec.
• You contribute video to a project that only accepts open formats.

Don’t convert to WebM for sharing a file with a person, for slide decks, video editors or phones’ photo libraries. Those expect MP4, and WebM support outside the browser is patchy.

MP4 vs WebM for websites

Will the WebM be smaller?

Often, but not always. VP9 is a more efficient codec than H.264, so at the same visual quality a WebM can come out smaller. How much depends on the video: screen recordings with large still areas compress very well in both formats, while busy camera footage benefits more. If your goal is mainly a smaller file, the video compressor gives you direct control with quality presets and a target size, and can write WebM too.

How to embed WebM with an MP4 fallback

For a self-hosted video on a web page, offer both files and let the browser pick the first one it can play:

1. Convert your MP4 to WebM here and keep the original MP4.
2. Upload both files next to each other on your site.
3. In the HTML video element, list the WebM source first and the MP4 second.
4. Add a poster image so the player isn’t blank before it loads. The video frame extractor saves any frame as an image.

For short, silent loops that replace GIFs, remove the sound first with mute video; browsers generally autoplay only videos without sound.

What gets converted

The video and sound are both re-encoded, because WebM can’t hold H.264 or AAC. This takes longer than a simple container change and loses a little detail, as any re-encode does. The size and orientation stay as they are. Encoding VP9 is more work for your computer than H.264, so expect a longer wait for long videos and keep the tab open.

Common mistakes

• Replacing the MP4 with the WebM on a site, then finding that a few visitors’ devices or an embedded player won’t play it. Keep both.
• Sending a WebM to a colleague who opens it in a desktop player or a slide deck. Send MP4 instead.
• Converting an already heavily compressed MP4 and expecting the WebM to look better. A conversion can’t restore detail that is gone.
• Renaming .mp4 to .webm. The file still holds H.264 and most players will reject it.

Tips

Start from the best source

Convert from the original export, not from an MP4 that was already compressed for chat or email.

Resize for the page

A video shown 800 pixels wide doesn’t need a 4K source. Use the video resizer first and the WebM will be smaller and faster to load.