Is my video uploaded anywhere?

No. ffmpeg.wasm runs locally in your browser. Your file never leaves your device.

Does it work on mobile?

Yes. Works on iPhone Safari (17.4+) and Android Chrome without installing any app.

Will WebM play everywhere?

WebM plays natively in Chrome, Firefox, Edge, Opera and modern Android. Safari on iOS 17.4+ also supports it. For older Safari or legacy hardware, use the MP4 converter instead.

Why is VP9 encoding so slow?

VP9 trades encoding time for compression efficiency — that is how it produces such small files. Expect roughly real-time encoding for short clips on a modern desktop.

Convert to WebM

Convert MP4, MOV, MKV, or AVI to WebM (VP9) for the web — smaller files, open format.

100% client-side · no upload

Video file (MP4, MOV, AVI, MKV…)

Settings Quality preset

Load a file to begin.

How to use

Choose your video file (MP4, MOV, AVI, MKV, or any other format).
Select a quality preset. Balanced (CRF 35) gives a good trade-off between quality and file size.
Click Convert to WebM. VP9 encoding is slower than H.264 — trim long videos first. Download the WebM result.

Related tools

More ways to use this tool

Frequently Asked Questions

Is my video uploaded anywhere?: No. ffmpeg.wasm runs locally in your browser. Your file never leaves your device.
Does it work on mobile?: Yes. Works on iPhone Safari (17.4+) and Android Chrome without installing any app.
Will WebM play everywhere?: WebM plays natively in Chrome, Firefox, Edge, Opera and modern Android. Safari on iOS 17.4+ also supports it. For older Safari or legacy hardware, use the MP4 converter instead.
Why is VP9 encoding so slow?: VP9 trades encoding time for compression efficiency — that is how it produces such small files. Expect roughly real-time encoding for short clips on a modern desktop.

Last updated: 2026-05-20 By jarvisbox