Convert WebM to MP4
Some editors and platforms still expect MP4. Drop your WebM below and vexo re-encodes it as MP4 (H.264 + AAC) entirely in your browser — no upload, no account.
Drop your video here
or choose a file from your device
Max 200 MB per file. Conversion runs in your browser.
Every conversion runs entirely in your browser. Your video never leaves your device.
About WebM → MP4
When should I convert WebM to MP4?
Many video editors (iMovie, older Premiere versions, mobile editors), social media uploaders, and older players don't accept WebM. MP4 with H.264 is the format every tool understands.
Will the file get bigger?
Usually slightly, because VP9 (WebM) compresses better than H.264 at the same perceptual quality. Push the quality slider to ~80 for a clean re-encode without doubling the size.
Is everything local?
Yes. vexo runs ffmpeg-wasm in your browser. The WebM never leaves your device; closing the tab erases everything.
What you're converting between
A short primer on both formats so the trade-offs are obvious before you hit Convert.
WebM
SourceWebM · introduced 2010
WebM was designed for the open web. VP9 typically produces 20–35% smaller files than H.264 MP4 at the same visual quality, and Opus is the best general-purpose audio codec available. Every modern browser (Chrome, Firefox, Safari 14+, Edge) plays WebM natively. vexo encodes WebM with VP9 + Opus, and falls back to VP8 + Vorbis automatically if the wasm bundle lacks VP9.
Strengths
- Smaller files than MP4 at the same perceived quality
- Royalty-free, open codec
- Native playback in every modern browser
Trade-offs
- Older video editors (iMovie, older Premiere) may reject it
- Some social uploaders and legacy players prefer MP4
- Slower to encode than MP4 in ffmpeg-wasm
MP4
TargetMPEG-4 Part 14 · introduced 2001
MP4 is the default video container of the modern web. With H.264 video and AAC audio it is the format every iPhone, Android phone, Windows machine, Mac, smart TV, video editor, social platform and browser understands without extra codecs. vexo encodes MP4 with the H.264 'veryfast' preset and 128 kbps stereo AAC — a safe default for talking-head, music and screen recordings.
Strengths
- Plays on every device and player on Earth
- Hardware-decoded on phones and laptops
- Compact at quality 70–80 for most content
Trade-offs
- Slightly larger than WebM at the same perceived quality
- H.264 has licensing concerns for some use cases (not for end-users)
Popular conversions
Each link below opens the converter pre-tuned for that conversion.
Supported formats
MP4 is the safest default for web and mobile playback. WebM gives the smallest files for modern browsers. GIF is for short, soundless animations.
WMV, FLV and other legacy/streaming formats are not supported in this version. Please convert those to MP4 first using a desktop tool.
| Format | Input | Output | Notes |
|---|---|---|---|
| MP4 | Yes | Yes | H.264 + AAC, broadest compatibility |
| MOV | Yes | No | Apple/QuickTime container; convert to MP4 |
| WebM | Yes | Yes | VP9 + Opus, smaller than MP4 |
| MKV | Yes | No | Container; convert to MP4 or WebM |
| AVI | Yes | No | Legacy container; convert to MP4 |
| GIF | Yes | Yes | No audio, short clips only |
| WMV | No | No | Not supported |
| FLV | No | No | Not supported |
Frequently asked questions
Your videos never leave your device
vexo is a static page. Every conversion runs inside your browser via ffmpeg compiled to WebAssembly. There is no server-side processing, no upload, no temporary file, no cache. When you close this tab, every file is gone.
- No account required.
- No server processing. Your videos stay on your device.
- No caching, no Service Worker, no IndexedDB persistence.
- The conversion engine (ffmpeg-wasm) is fetched from a public CDN and cached by the browser; no personal data is sent.