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WebM to MP4 Converter — Free, Online, No Upload

Turn a WebM screen recording or web download into an MP4 that phones, editors and upload forms accept — converted on your device, never uploaded.

Free · no signup2 free files a day100% in-browser · no upload

Tap to select WEBM files

or click to browse

2 free files per day (2 left today) · Up to 10 MB each · Upgrade for more

✓ Files never uploaded✓ 100% browser-based✓ No account required
Need the reverse?MP4 → WEBM

How to convert WEBM to MP4 online

  1. 1

    Drop your WEBM file

    Drag your WebM Video Format file onto the box above, or click it to pick a file.

  2. 2

    Wait while it converts

    Conversion starts on its own and runs on your device, not on a server. Video takes roughly as long as the clip plays, so keep the tab open.

  3. 3

    Download your MP4

    Click Download to save the MPEG-4 Part 14 file.

WEBM vs MP4: format overview

WEBM

WebM Video Format

Google (On2 Technologies) · 2010

Compression
lossy
Transparency
No
  • ✓ Royalty-free codec (VP8/VP9/AV1)
  • ✓ Excellent web streaming support
  • ✗ Not supported on iOS/Safari natively
MP4

MPEG-4 Part 14

Moving Picture Experts Group · 2001

Compression
lossy
Transparency
No
  • ✓ Universal compatibility across all platforms
  • ✓ Excellent compression with H.264/H.265

WEBM magic bytes: 1A 45 DF A3

MP4 magic bytes: 00 00 00 xx 66 74 79 70

Why convert WEBM to MP4?

WebM is the web's own video format. Browser screen recorders and tools built on the browser's recording feature often save .webm files, and many sites serve video as WebM too.

Browsers are fine with it: Chrome, Firefox and Edge play WebM, and recent versions of Safari on Mac and iPhone play many WebM files. Outside the browser it's patchier. Many video editors won't import it (Adobe Premiere Pro needs a plug-in), phone apps often can't open it, and many upload forms and older TVs reject it.

MP4 with H.264 video and AAC sound is the version almost everything accepts. Converting takes your WebM's VP8 or VP9 video and Opus or Vorbis sound and re-encodes them into that combination.

Going the other way? Use MP4 to WebM. Need only the sound? WebM to MP3 skips the video.

Common reasons to convert WebM to MP4:

  • ›Sharing a screen recording with someone on an iPhone or Mac
  • ›Editing a recording in a video editor that won't import WebM
  • ›Uploading to a site or app that only accepts MP4
  • ›Keeping a copy that plays on TVs and older devices

Quality & file size: WEBM to MP4

This is a re-encode, not a copy: MP4 can't hold WebM's VP8 and VP9 video, so the picture is rebuilt as H.264 (CRF 23) and the sound as 192 kbps AAC. CRF 23 looks the same as the source for most screen recordings and everyday video. Very detailed, high-bitrate footage can lose a little fine texture.

In our test on production, a 46.6-second 960×400 WebM (VP9 video, Opus sound, 17.2 MB) became a 15.7 MB MP4 in about 45 seconds in Chrome on a Mac. The length and frame rate stayed the same. Expect roughly real time: about a minute of work per minute of video, more for 1080p and above on slower devices.

Screen recordings often have odd sizes like 1365×767. H.264 needs even numbers, so the converter adds one pixel where needed instead of failing.

WebM files with AV1 video, which some YouTube downloads use, can't be decoded by this converter yet. You get a message saying so, not a broken file.

The free tier takes files up to 10 MB, so many recordings longer than a minute need Pro, which takes files up to 500 MB.

Frequently asked questions

How do I convert WebM to MP4?
Drop the .webm file on this page. The video is re-encoded to H.264 and the sound to AAC in your browser, and the MP4 downloads when it's done. Nothing is uploaded.
Is WebM or MP4 better?
For sharing, MP4: almost every phone, editor and site accepts it. WebM's VP9 video can be a bit smaller at the same quality and it's the web's open format, but outside browsers it's poorly supported.
Why won't my WebM play on my iPhone?
Recent Safari can play many WebM files, but other iPhone apps often can't. Convert it to MP4 here and it plays in the phone's own apps, and you can save it to Photos.
What is a WebM file?
A video file in the WebM format, an open format backed by Google. It holds VP8, VP9 or AV1 video and Opus or Vorbis sound. Browsers play it; many other apps don't.
How long does converting take?
Roughly as long as the video. Our 46-second test took about 45 seconds in Chrome on a Mac. Longer and higher-resolution videos take longer, and the tab needs to stay open.
Why does my WebM fail to convert?
The most common reason is AV1 video, which this converter can't decode yet. You'll see a message saying so. HandBrake (free) or VLC can convert AV1 WebM files on your computer.
How can I play a WebM without converting it?
Open it in Chrome, Firefox or Edge, or install the free VLC player, which plays WebM on Windows, Mac, iPhone and Android.

Your WEBM file never leaves this tab — FormatDrop has no endpoint that receives file data. How it works