Skip to content
convertexa

MP4 → WebM

MP4 to WebM converter

convertexa converts MP4 files to WebM locally in your browser using a dedicated ffmpeg engine. Nothing is uploaded: the file is read, converted and handed straight back to you as a download.

  • Free, no sign-up
  • Nothing is uploaded
  • Works offline
Quality
Re-encoded
Runs
In your browser
Max input
300 MB
Status
stable

Drop a file to convert

Everything happens on your device — nothing is uploaded.

or paste with Ctrl+V

How to convert MP4 to WebM

  1. 1 Drop your MP4 file here.
  2. 2 Choose WebM as the output format and adjust the options.
  3. 3 Convert and download the result.

About MP4 and WebM

MP4 with H.264 video is the safest format for browsers and phones.

WebM uses VP8/VP9 and Opus, and is natively supported by browsers.

MP4 files are read by the convertexa engine that ships with this page, so the conversion is identical whether you use this tool or the general converter. The output is produced with the same codec settings for every visitor, which means the same input always produces the same result.

Limitations

  • Re-encoding a lossy source cannot restore the quality that was lost when it was first encoded.
  • WebM output uses VP8 video and Opus audio; the VP9 encoder is not available in the single-threaded WebAssembly build.

Frequently asked questions

How do I convert a MP4 file to WebM?

Add your MP4 file to the box above. convertexa detects the format from the file content, applies the MP4 to WebM conversion and gives you the result to download. The whole operation runs inside your browser.

Are my MP4 files uploaded anywhere?

No. The conversion runs in a sandboxed worker on your own device. Your file never leaves the browser, and nothing is stored on a server.

Is the MP4 to WebM conversion lossless?

No. WebM is a re-encoded format, so some data is discarded to reach the target format. MP4 with H.264 video is the safest format for browsers and phones.

Is there a size limit?

For reliable results keep the input under 300 MB. Very large files run out of memory in the browser rather than failing quietly.

Which browsers are supported?

Any current version of Chrome, Edge, Firefox or Safari on a desktop. The conversion engines need WebAssembly and Web Workers, both of which are standard since 2018.