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WebM to MP4 Converter

Turn a WebM into an MP4 that editors, phones and televisions will actually play.

Converters Reviews Free · no sign-up

Drop a WebM here, or click to choose one

Converted on your device — the video is never uploaded

Result

Quick Tool Overview

The WebM to MP4 Converter re-encodes VP8 or VP9 video to H.264 in an MP4 with faststart metadata, so editors, phones and televisions will finally play it.

What it does
Converts WebM video to MP4
You give it
A .webm or .mkv file
You get back
An H.264 MP4
Best for
Screen recordings and downloaded clips
Converters Free, unlimited use No sign-up Runs in your browser

About the WebM to MP4 Converter

WebM is a web format. Browsers love it, and almost nothing else does: iPhones refuse it, televisions ignore it, and most video editors will not import it. A screen recording, a downloaded clip or an exported animation in WebM often has to become an MP4 before it is any use.

The conversion runs in your browser through ffmpeg.wasm — the real ffmpeg, compiled to WebAssembly. Nothing is uploaded: a wedding video, a client recording or an unreleased track never leaves your machine. The engine is a one-off download of about 32 MB, after which your browser caches it and every later conversion starts immediately.

The video is re-encoded from VP8 or VP9 to H.264 and the audio to AAC, in an MP4 with the metadata moved to the front so it starts playing before it has finished downloading. Choose the quality, the encoding speed, a smaller resolution or frame rate, trim to a section, or drop the audio. Encoding video in a browser is slower than a desktop app — the page tells you when a clip is long enough for that to matter.

Key features of the WebM to MP4 Converter

Quality and speed control

From visually lossless to small, fast to thorough.

Resize and reframe

Scale to 1080p or 720p and change the frame rate.

Faststart

Metadata is moved to the front so the video starts playing sooner.

Trim as you convert

Give a start time and a length to take just the part you need.

Nothing is uploaded

ffmpeg runs inside the browser tab, so the file never leaves your computer.

How to use the WebM to MP4 Converter

  1. 1

    Drop the WebM in

    MKV works here too.

  2. 2

    Choose quality and speed

    Good quality at Fast suits most clips.

  3. 3

    Resize or trim if you want

    A smaller size encodes much faster.

  4. 4

    Convert and download

    An MP4 everything plays.

Frequently asked questions

Roughly real time to a few times real time, depending on the resolution and your computer. A 30-second clip is quick; a 20-minute recording takes a while, so leave the tab open.

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