Why WebM?
WebM is an open, royalty-free video format designed for the web. Web developers use it for HTML5 video backgrounds, embedded clips and web apps, often alongside MP4 as an alternative source. Some platforms and tools, such as certain sticker or animation features, specifically ask for WebM.
Things to consider
Encoding to WebM is computationally heavy and runs on your own device, so long or HD videos can take quite a while – short clips are fastest. Not every device or editor plays WebM, particularly older Apple devices, so keep your MP4 for general sharing. Quality stays close to the original.
How to convert
Drop your MP4 above, WebM is preselected, click “Convert” and download. FFmpeg does the encoding locally in your browser, without any upload.