Why convert MP4 to WebM?

WebM is an open format for the web. Some sites, HTML5 players, and tools require it, and it avoids patent-encumbered codecs.

Will the WebM be smaller?

Often it is similar. VP9 and AV1 are efficient, but the size depends on the bitrate the encoder chooses for your video.

MP4 to WebM

Convert an MP4 video to WebM for the web. Processing stays on your device.

Files stay on your device

Drop a file to convert

See its format, then choose an output.

Any media file this browser’s engine can read.

How to convert MP4 to WebM online

Open an MP4 and export a WebM for a website, a game engine, or anywhere an open format is required. The MP4 to WebM converter re-encodes H.264 video to a WebM codec and AAC audio to Opus in your browser, without uploading the file.

Step 1
Choose your MP4
Pick a file or drop it into the converter above.
Step 2
Keep WebM
WebM is selected; choose another format if you need one.
Step 3
Download the WebM
Save the WebM when the conversion finishes.

What to expect

Supported inputs: MP4 videos and other readable video files.
What happens: H.264 and HEVC video is re-encoded to VP9, AV1, or VP8, whichever this browser can encode, and audio to Opus. VP9 or AV1 video already in the MP4 is copied.
Limits: Re-encoding takes longer than copying and depends on your device. An HEVC MP4 needs a browser that can decode HEVC.

Private by design

Your video stays on your device

Mastershot processes your file locally in this browser. It does not need to be uploaded to a server, and you do not need an account to use the tool.

No upload
No signup
No watermark