Convert MP4 to WebM

Convert MP4 to WebM with VP9 video and Opus audio, an open format made for the web. The conversion runs in your browser, so nothing is uploaded.

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What is WebM?

WebM is an open, royalty-free video container built for the web. It pairs VP9 video with Opus audio. Every modern browser plays it without plugins.

How to convert MP4 to WebM

Drop an MP4, M4V or MOV above and press Convert. When your browser offers a VP9 encoder through WebCodecs, MediaBunny uses it, which is the fastest path. Otherwise FFmpeg encodes VP9 at CRF 34 with a real-time speed setting, and the audio becomes Opus at 128 kbps. Download the WebM when the progress bar finishes.

Why convert MP4 to WebM?

WebM often gives similar quality at a smaller size than H.264 MP4. That makes it a common choice for background videos, HTML5 players and open-source projects. Wikipedia and other sites that only accept open formats also ask for WebM.

About encoding speed

Video encoding runs in this browser tab, on your own device. There is no upload and no queue. Your device does all the work, so a large or long clip can take a minute or more. VP9 needs a lot of processing, so short clips convert fastest.

Before you start

Input: MP4, M4V, and MOV. Output: WebM. The settings appear before anything runs, so you can check them first. Your original file is never changed.

Video work uses a lot of memory and CPU. Try a short clip first and check that the sound and playback work. On a phone, split large batches into smaller ones.

Keep the original until you have opened and checked the result. The work happens in this browser tab, so the size you can handle depends on your device's memory, your browser and the file itself.