How to convert WebM to MP4
Drop your WebM files into the box above, or click Choose files. You can add several at once.
Choose a quality. It only matters if the video has to be re-encoded; compatible videos are copied without any loss.
Click Convert to MP4. Files are processed on your device; a few minutes of media usually takes seconds.
Download the MP4 files one by one, or all at once as a ZIP.
Why convert WebM to MP4?
WebM is the web's open video format, and many screen recorders and browser-based tools save to it. But iPhones, many Windows apps, PowerPoint and video editors like Premiere don't handle it well.
MP4 with H.264 video and AAC audio plays everywhere and is accepted by every upload form and social platform.
Screen recordings often show private work: emails, dashboards, customer data. Converting on your device keeps them private.
WebM vs MP4
WebM usually contains VP8 or VP9 video with Opus audio. Those codecs aren't what most MP4 players expect, so the video is re-encoded to H.264 and the audio to AAC.
Re-encoding takes longer than a simple rewrap. It usually runs in real time or faster with hardware acceleration, and the Quality setting balances size against sharpness.
| Property | WebM | MP4 |
|---|---|---|
| Typical video codec | VP8, VP9 or AV1 | H.264 (AVC), sometimes H.265 or AV1 |
| Typical audio codec | Opus or Vorbis | AAC |
| File size | Efficient | Efficient |
| Best for | Video embedded in web pages, screen recordings | Sharing and uploading video anywhere |
| Support | Chrome, Firefox, Edge; limited in Apple and Windows apps | Every phone, browser, TV and editing app |
Is it safe?
Yes. WebM to MP4 runs entirely in your browser. Your files are read and converted by your own device using built-in browser technology, so they are never uploaded to a server and nobody else can see them.
You can check this yourself: open your browser's developer tools, switch to the Network tab and convert a file. No upload requests are made.
Videos are processed by your browser's own media engine (WebCodecs), usually with hardware acceleration. Nothing is uploaded, which also makes the conversion start instantly, however big the file.
Files stay in this tab's memory only until you remove them or close the page.
Frequently Asked Questions
Why won't my WebM play on my iPhone or in PowerPoint?
Support for WebM's VP9 video and Opus audio is limited outside browsers. MP4 with H.264 and AAC is the combination every device and app supports.
Which quality setting should I use?
High keeps screen text sharp and is the default. Medium works well for camera footage. Small file suits quick previews or strict upload limits.
Which browser works best?
Current Chrome, Edge and Safari support hardware video encoding and decoding. Firefox works for most files but can't decode HEVC. If a file can't be processed, you'll see a message saying why.
Why does WebM take longer than MOV or MKV?
WebM's VP9 video can't simply be copied into an MP4 for broad playback, so every frame is re-encoded to H.264. With hardware encoding that usually runs faster than the video's own length, and the progress bar shows how far along each file is.
Is there a size limit?
Each video can be up to 1 GB. Files are read from disk in pieces, so they don't need to fit in memory, but very long videos take longer on slower devices.