MP4 to WebM Converter
Convert MP4 videos to WebM format in your browser.
Drop your MP4 file here
or click to browse · max 500 MB
Settings
128k for speech · 192k for general use · 320k for music
FFmpeg WASM (~25MB) will be downloaded on first use and cached by your browser.
MP4 to WebM Converter
Converts MP4 video files to WebM format using VP9 codec. WebM is an open, royalty-free media format developed by Google, optimized for web playback. VP9 offers excellent compression efficiency, often producing smaller files than H.264 at similar quality levels.
What is it used for?
- Web video embedding with HTML5 <video> tag for faster loading
- Reducing bandwidth usage on websites with video content
- Open-source projects requiring royalty-free video formats
- Progressive web apps and offline-capable video players
- YouTube and web platform compatibility
Step-by-Step Guide
- Click the upload area or drag and drop your MP4 file
- Adjust VP9 CRF quality (15-63) in the settings panel
- Click 'Convert to .WEBM' to start the conversion
- Wait for FFmpeg WASM to process (progress bar shown)
- Preview the result and click Download
How it works
Upload an MP4 file and click Convert. FFmpeg WASM runs entirely in your browser using VP9 encoding with CRF 30 for optimal quality-to-size ratio. The converted WebM file can be previewed and downloaded instantly. No data ever leaves your device.
MP4 (H.264) vs WebM (VP9)
| Feature | MP4 (H.264) | WebM (VP9) |
|---|---|---|
| Compression | Good | Better (20-50% smaller) |
| Browser Support | All browsers | Chrome, Firefox, Edge |
| Royalties | Patent-encumbered | Royalty-free |
| Mobile Support | Universal | Android, most iOS |
| Encoding Speed | Fast | Slower |
Tips & Best Practices
- For web embedding, WebM with VP9 can save 20-50% bandwidth compared to H.264
- Use CRF 20-25 for high-quality archival, CRF 30-40 for web delivery
- Short clips (under 5 minutes) convert fastest in the browser
Frequently Asked Questions
Is WebM better than MP4 for the web?
WebM with VP9 generally provides better compression for web delivery, resulting in smaller files at similar quality. However, MP4 (H.264) has wider device support. Use WebM for web-focused content and MP4 for maximum compatibility.
Will I lose quality converting MP4 to WebM?
Since both are lossy formats, there is always some quality change when transcoding. The default CRF 30 setting maintains good visual quality. Lower CRF values (closer to 15) preserve more quality at the cost of larger files.
How long does the conversion take?
Conversion time depends on file size, video length, and your device's CPU. A 1-minute video typically takes 30-90 seconds. The FFmpeg WASM library (~25MB) is downloaded once and cached by your browser.
Is there a file size limit?
Files up to 500MB are supported. Files over 100MB will show a warning as they may require more memory and processing time.
Privacy & Security
This tool uses FFmpeg compiled to WebAssembly (WASM). The WASM binary (~25MB) is downloaded from a CDN on first use and cached by your browser. All file processing happens locally on your device - your files are never uploaded to any server. This makes it safe for sensitive, private, or confidential media files. Large files may take longer to process depending on your device's CPU and available memory.