WebM to MP4 Converter

Free, no sign-up. Your video never leaves your device.

Video quality
Frame size

MOV and MKV with H.264 and AAC are repackaged into MP4 without re-encoding — fast and lossless. Everything else is re-encoded in your browser, which is slow: a minute of video takes from tens of seconds to a few minutes. 720p means the short side of the frame is 720 pixels.

Usage statistics

We count page views and operations. A random cookie identifies a browser profile; after sign-in its activity is linked to your account. Your last IP and its observation date are visible only to the site owner and kept for up to 90 days. Daily counts are kept for 90 days, and inactive profiles are removed after 90 days. Formats, outcomes, error codes, and size and time ranges are counted separately. File names, contents and metadata stay on your device. Turning this off deletes the current browser profile.

How to convert WebM to MP4

  1. Click the box above or drag your WebM files onto it — you can add many at once.
  2. Wait while your browser processes the video — nothing gets uploaded. Progress is shown as a percentage.
  3. Download each MP4 separately or grab them all in one ZIP file.

Why use this converter

  • Your video stays with you

    Conversion runs on your device. Your video is never uploaded, so nobody but you can see it.

  • H.264 and AAC

    VP9 or VP8 video is re-encoded to H.264 and Opus audio to AAC, so iPhones, Windows, TVs and editors can open the MP4.

  • Pick quality and size

    Choose the quality and frame size — from original down to 480p — to make the file smaller.

  • Many files at once

    Add several videos at a time and download them one by one or as a single ZIP.

Frequently asked questions

What is WebM?

WebM is Google's open video format, usually VP9 or VP8 video with Opus audio. YouTube, browser screen recorders and many websites use it. iPhones, older TVs and some editors can't open it, while MP4 works everywhere.

What happens to the video and audio?

The video is re-encoded to H.264 and the audio to AAC — the standard MP4 pairing that virtually every device supports.

Why does it take a while?

Re-encoding video is heavy work, and it happens right on your device. A minute of video takes from tens of seconds to a few minutes, depending on resolution and your computer. Progress is shown as a percentage.

How do I make the file smaller?

Choose “Medium” or “Low” quality and a smaller frame size — 720p or 480p. 720p means the short side of the frame is 720 pixels: for a vertical video that's the width.

Do screen recordings work?

Yes. Screen recordings made in the browser and by some apps are saved as WebM — the converter turns them into MP4 you can share anywhere.

Which browsers does it work in?

Up-to-date Chrome, Edge, Firefox and Safari: video is encoded with the browser's built-in codecs (WebCodecs). If your browser lacks a codec, the file's row will tell you.

Is it safe?

Yes. Only the converter itself is loaded from the site; your video is processed in your browser and never sent to a server.

More converters