BrowserTools

MP4 to WebM Converter

Re-encode videos to the open WebM format

By Guga — BrowserTools maintainer, Tbilisi, Georgia Updated 2026-09-06
Free Private No uploads

One-time cost first: a roughly 30 MB FFmpeg build is fetched from unpkg.com the first time this page converts anything, then served from the browser cache. Video and audio are re-encoded inside the tab and never uploaded.

What is MP4 to WebM Converter?

WebM is the open, royalty-free container, and this produces a real VP8 video stream with Vorbis audio inside it — not an MP4 with the extension changed. The catch is that the bitrate is pinned. Every conversion targets 1 Mbps for video, so at 1080p30 that works out to about 0.016 bits per pixel per frame, which is a thin budget and will look visibly softer than a well-encoded H.264 original; at 720p the same budget buys roughly 0.036 bits per pixel, which is usable for web embedding. The audio is re-encoded too, so a lossless master loses that on the way through. There are no quality or resolution controls here — for a fixed-budget web embed, run it; for archival, keep the original file.

Convert MP4 videos to WebM — the open, royalty-free format used widely on the web. Quality and size settings included, and conversion runs fully in your browser.

Private MP4 to WebM Converter In Your Browser

MP4 to WebM Converter is processed locally with client-side JavaScript. Your files never touch a server, and there is no queue to wait in.

Step-by-Step

How to use MP4 to WebM Converter

1

Drop a source clip onto the panel — MP4, MOV, MKV, AVI and WebM are all handled.

2

Leave the settings alone — the target bitrate is fixed at 1 Mbps with Vorbis audio at quality level 4.

3

Press Convert to WebM, allowing for a one-off engine download the first time you use any converter on this site.

4

Watch the result in the embedded video player and download it with the button beneath the size comparison.

Key Capabilities
  • Produces genuine VP8 video and Vorbis audio in a WebM container rather than a renamed MP4.
  • Uses a fixed 1 Mbps video target, so the output size is predictable from the source duration before you convert.
  • Accepts MP4, MOV, MKV, AVI and WebM as input, covering most phone, camera and screen-recording sources.
  • Previews the finished file in a video element before you download it.
Common Use Cases
  • A front-end developer adding a short product clip to a page that must not ship patent-encumbered video codecs.
  • A course creator replacing screen recordings with a smaller WebM so the lesson page loads faster on mobile data.
  • A hobbyist checking whether a WebM copy of their footage is an acceptable size for a forum attachment.
Clear Answers

Frequently Asked Questions

Why is my converted WebM softer than the original MP4?
Because 1 Mbps is the only video setting on this page. A 1080p clip at that budget gets roughly 0.016 bits per pixel per frame, and modern codecs need considerably more than that to look transparent. This page is built for embedding a preview on a web page, not for repackaging a master.
Can I raise the bitrate or choose a different codec?
No. The encode command is fixed at libvpx with a 1 Mbps target and libvorbis audio at quality 4, and the interface exposes no controls for it. If bitrate matters, convert the source to a lower-resolution MP4 first so the fixed budget has less to describe.
Will my original audio quality survive?
No. Audio is re-encoded to Vorbis, so an AAC or FLAC soundtrack is compressed again on the way out. Compression applied twice is more visible than once, particularly on cymbals and high-frequency detail.
Does this need the large download before the first attempt?
Yes. A roughly 30 MB WebAssembly build of FFmpeg comes from unpkg.com the first time this page converts anything, then stays in the browser cache. The video itself is re-encoded in the tab and never uploaded.