Free WebM to MP4 converter

How do I convert WebM to MP4?

Add the WebM file above, keep MP4 as the output and click convert. The video is re-encoded to H.264 with AAC audio on your own device, and you download an MP4 that plays in almost any app, player or upload form. Nothing is uploaded.

Where do WebM files come from?

WebM is the web’s own video format, and browsers are the main source of WebM files. When a website records your screen, camera or microphone, it usually uses the browser’s built-in recorder, and in Chrome, Edge and Firefox that recorder usually writes WebM. So you’ll often get WebM from:

• Browser-based screen recorders and extensions
• Video messages and recordings made in web apps
• Videos saved from websites that serve WebM
• Exports from tools that default to an open format

Why won’t my WebM file play?

WebM plays fine in browsers, but many other places expect MP4. Common trouble spots are PowerPoint and Keynote, the Photos app on iPhone, some Windows players, video editors, LMS platforms and upload forms that list “MP4, MOV” only. The reason is the codecs inside: WebM holds VP8, VP9 or AV1 video and Opus or Vorbis audio, while those apps are built around H.264 and AAC.

Because the codecs differ, WebM to MP4 is a real re-encode, not just a new file extension. Renaming a .webm file to .mp4 doesn’t work: the extension changes, the contents don’t, and most players still refuse it.

Recordings with odd lengths or no seeking

WebM files written by a browser recorder are saved as the recording happens, so they sometimes lack the index that tells a player how long the video is. The video then shows no duration, or the seek bar jumps around. Converting to MP4 writes a complete file with a proper index, so the duration shows and you can skip to any point. The MP4 is also saved with its index at the start, so it can begin playing on a web page before it has fully loaded.

Does WebM to MP4 lose quality?

Any re-encode loses a little detail, but at the default settings it is hard to see, especially for screen recordings where most of the picture stays still. The file size may go up or down: VP9 is an efficient codec, so an MP4 of the same quality can be somewhat larger. If size matters, run the MP4 through the video compressor afterwards, or trim it first with the video trimmer.

When you can keep WebM

You don’t always need to convert. If the video only ever plays on a web page, in a browser-based tool or in a help center that accepts WebM, keep the original and skip a re-encode. Convert when the file has to work outside the browser: in a slide deck, an editor, a phone’s photo library, an email attachment someone opens on their phone, or an upload form that lists MP4. When in doubt, MP4 is the safer file to send, because the person receiving it never has to think about formats.

Tips for screen recordings

Cut before you share

Browser recordings often start with a few seconds of picking a tab and end with clicking stop. Trim those away so the video starts where the action does.

Mind what’s on screen

Screen recordings show tabs, bookmarks and notifications. Because this tool runs on your device, nothing leaves it while you convert, but check the video before you send it on.

Need the other direction?

To make an MP4 for a web page in an open format, use MP4 to WebM. For other formats, the video converter handles MOV and MKV too.