WebM to MP4 Converter
Convert WebM to MP4 free — no upload, no signup
To convert WebM to MP4, drop your WebM video into the box below and click Convert. Fylo converts with ffmpeg running inside your browser, so nothing is uploaded and there's no signup or watermark. VP9 or VP8 WebM is re-encoded to H.264 MP4 that plays everywhere.
Drop videos here
or tap to browse · paste with Ctrl+V · add many at once
Your files never leave your device
If the video already uses codecs that fit the new format, Fylo repackages it instantly with no quality loss.
Advanced
How to convert WebM to MP4
Add your WebM videos
Drag and drop WebM files into the box or tap to choose them. The converter engine (about 31 MB) downloads once, the first time you convert.
Choose quality (optional)
Balanced quality suits most videos. If the codecs already fit MP4, Fylo repackages the file instead of re-encoding it, with no quality loss.
Convert and download
Click Convert, then download each MP4 file or all of them as one ZIP.
Why convert WebM to MP4?
Browser screen recordings, downloads and web videos are often WebM, which Premiere Pro, iMovie, WhatsApp, Instagram and many TVs reject. MP4 works in all of them.
What happens when you convert WebM to MP4?
WebM's VP8/VP9 video isn't allowed in MP4 for most players, so Fylo re-encodes it to H.264 and converts Opus or Vorbis audio to AAC. File size is often similar to the WebM. Encoding runs on your device — a 1-minute 1080p recording typically takes a minute or two on a laptop.
How does Fylo convert WebM to MP4?
Fylo reads the WebM with ffmpeg compiled to WebAssembly and writes H.264 (x264, constant quality CRF 23) with AAC audio, plus the faststart flag for instant web playback. WebM's usual codecs (VP8, VP9, AV1) can't go into MP4 as-is, so the video is re-encoded. Speed depends on your device: short phone clips take seconds, while on our slow test PC a 2-minute 1080p video took about 10 minutes. Only the first video and audio track are kept, and the original resolution is preserved unless you pick 1080p, 720p or 480p under Advanced.
What's the difference between WebM and MP4?
WebM was announced by Google in 2010 as an open, royalty-free alternative to H.264 for HTML5 video. It's a subset of Matroska restricted to VP8, VP9 or AV1 video and Vorbis or Opus audio. Browser screen recorders and many web tools save WebM by default.
MP4 (MPEG-4 Part 14) is a container format standardised in 2001 and based on Apple's QuickTime file structure. A container holds separately compressed video and audio streams plus metadata such as subtitles, chapters and cover art. Most MP4s use H.264 video and AAC audio; newer files may use H.265 (HEVC) or AV1.
Learn more: WebM format guide · MP4 format guide
| Property | WebM | MP4 |
|---|---|---|
| Developed by | MPEG (ISO/IEC 14496-14) | |
| Introduced | 2010 | 2001 |
| Typical video codecs | VP8, VP9, AV1 | H.264, H.265/HEVC, AV1 |
| Typical audio codecs | Vorbis, Opus | AAC, MP3 |
| Plays in web browsers | Yes — Chrome, Edge, Firefox, Safari 14.1+ | Yes — every browser |
| Compatibility | Browsers, Android; limited in editors and on iPhone apps | Universal: phones, TVs, editors, social media |
| Best for | Royalty-free web video, screen recordings | Sharing, uploading, streaming, editing |
Frequently asked questions
Why do screen recorders make WebM?
Browsers' built-in recorders produce WebM because VP8/VP9 are royalty-free. Converting to MP4 makes the recording easy to share and edit.
Can I upload WebM to Instagram?
Instagram and WhatsApp expect MP4 — convert first.
Is my WebM file uploaded to a server?
No. Fylo runs ffmpeg, the same engine used by professional video tools, compiled to WebAssembly inside your browser. Your WebM file is read directly from your device and never sent anywhere.
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