# Convert WebM to MP4

WebM files from screen recorders, browsers and downloads often will not open on an iPhone, in PowerPoint or in video editors. Convert them to an MP4 that opens everywhere.

_Source: https://sharelargefilesfree.com/tools/webm-to-mp4 · Updated 2026-09-29_

## How to use it

1. Choose one or more WebM files.
2. Keep “Plays everywhere” (recommended for WebM).
3. Press Convert WebM to MP4 and wait for the progress bar.
4. Download the MP4 files or send them with a link.

## Why WebM needs a real conversion

WebM holds VP8, VP9 or AV1 video with Opus or Vorbis sound, codecs made for the web. Plenty of software does not play them, so the video is re-encoded to H.264 and the sound to AAC. That takes about as long as the video plays on a phone, and much less on a computer with hardware acceleration.

Choosing “Fastest” copies VP9 or AV1 into the MP4 without re-encoding. That is instant but only helps if your player supports those codecs, so it is not the default here.

## Screen recordings

Browser-based screen recorders and tools such as OBS (with WebM output) produce WebM files with a variable frame rate. The conversion keeps the timing of every frame, so the sound stays in sync. For a smaller file to share, run the MP4 through [Compress video](https://sharelargefilesfree.com/tools/compress-video), or make a short loop with [Video to GIF](https://sharelargefilesfree.com/tools/video-to-gif).

## Private by design

Screen recordings often show emails, documents and chats. Here they never leave your device: the conversion runs in your browser and nothing is uploaded unless you choose to share the result.

## Frequently asked questions

### Why won't my WebM play on iPhone or in PowerPoint?

They do not support every WebM codec. Converting to MP4 with H.264 video and AAC sound fixes that.

### How long does converting WebM to MP4 take?

Roughly real time or faster: a five-minute recording takes a few minutes on a phone and usually well under that on a computer.

### Is the sound converted too?

Yes. Opus or Vorbis sound is converted to AAC at 160 kbps so it plays everywhere.

### Are my recordings uploaded?

No. They are converted on your device.