MP4 → WebM

Convert MP4 to WebM

WebM (VP9 + Opus) gives you smaller files than MP4 at the same perceived quality, perfect for HTML5 video on the modern web. Drop your MP4 below and vexo re-encodes it to WebM directly in your browser — nothing is uploaded.

Drop your video here

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Supports MP4, MOV, WebM, MKV, AVI, GIF and more

Every conversion runs entirely in your browser. Your video never leaves your device.

About MP4 → WebM

Why convert MP4 to WebM?

WebM with VP9 typically produces 20–35% smaller files than H.264 MP4 at the same visual quality. For HTML5 <video> elements served from your own site, that means faster page loads, lower CDN bills and better Core Web Vitals. Every modern browser plays WebM natively.

What's the right quality setting?

Around 70 is a sensible default. Drop to 50–60 for thumbnails or short loops where size matters more than fidelity; push to 85+ for hero videos. The quality slider maps to VP9's CRF internally, so the trade-off is well-tuned.

Is my MP4 uploaded anywhere?

No. vexo loads ffmpeg compiled to WebAssembly into your browser and runs the transcode locally. The file never leaves your device, and closing the tab erases everything.

Each link below opens the converter pre-tuned for that conversion.

Supported formats

MP4 is the safest default for web and mobile playback. WebM gives the smallest files for modern browsers. GIF is for short, soundless animations.

WMV, FLV and other legacy/streaming formats are not supported in this version. Please convert those to MP4 first using a desktop tool.

Format	Input	Output	Notes
MP4	Yes	Yes	H.264 + AAC, broadest compatibility
MOV	Yes	No	Apple/QuickTime container; convert to MP4
WebM	Yes	Yes	VP9 + Opus, smaller than MP4
MKV	Yes	No	Container; convert to MP4 or WebM
AVI	Yes	No	Legacy container; convert to MP4
GIF	Yes	Yes	No audio, short clips only
WMV	No	No	Not supported
FLV	No	No	Not supported

Frequently asked questions

Is this video converter free?

Yes. vexo is free to use, no account is required, and there are no paid plans.

Are my videos uploaded to a server?

No. vexo runs entirely in your browser using ffmpeg compiled to WebAssembly. Your videos are never uploaded, never seen by our infrastructure, and never stored anywhere outside your device. When you close the tab, every file is gone.

Which formats are supported?

Inputs: MP4, MOV, WebM, MKV, AVI, MPEG, 3GP, OGV and GIF. Outputs: MP4 (H.264 + AAC), WebM (VP9 + Opus) and animated GIF.

Why does the first conversion take a moment?

The first time you convert a video, vexo downloads the conversion engine (about 25 MB). After that it stays in your browser cache, and subsequent conversions start immediately.

Is there a file size limit?

Yes. Each file may be up to 200 MB. Browser memory is the real ceiling — very large 4K clips may struggle on lower-end devices.

Can I trim or resize the video?

Yes. You can set a start/end time to trim and pick a target width (1080p, 720p, 480p, 360p or original).

How long does a conversion take?

Depends on the video. A 1-minute 1080p MP4 typically converts in 1–3 minutes on a modern laptop. Mobile is slower. The progress bar shows real-time progress.

Why is my converted file bigger than the original?

If you raise the quality slider above the source's encoder settings, the output can grow. Lower the slider toward 50–70 for noticeable shrink, or trim/resize to drop the bitrate further.

Can I convert multiple videos at once?

Not yet. Video encoding is memory-heavy, so vexo converts one file at a time. Batch support may come later.

Are ads required to use the tool?

No. Ads are isolated from the converter. The tool works completely even if ads fail to load or are blocked.

Your videos never leave your device

vexo is a static page. Every conversion runs inside your browser via ffmpeg compiled to WebAssembly. There is no server-side processing, no upload, no temporary file, no cache. When you close this tab, every file is gone.

No account required.
No server processing. Your videos stay on your device.
No caching, no Service Worker, no IndexedDB persistence.
The conversion engine (ffmpeg-wasm) is fetched from a public CDN and cached by the browser; no personal data is sent.