How to convert MP4 to WebM
- Drop your MP4 file.
- Adjust quality, resolution or bitrate if you want (defaults are optimized).
- Optionally set a start time and duration to trim.
- Click Convert, watch the progress and download your WebM file.
Why convert MP4 to WebM?
MP4 is excellent for sharing, uploading and playing video anywhere, but it has some limitations:
- Lossy compression
- Re-encoding reduces quality slightly
Converting to WebM gives you:
- Royalty-free and open
- Great for HTML5 video
- Small files
MP4 vs WebM: side-by-side comparison
| Feature | MP4 | WebM |
|---|---|---|
| Full name | MPEG-4 Part 14 | WebM Video |
| File extension | .mp4 | .webm |
| Type | Video | Video |
| Compression | Lossy (H.264/H.265) | Lossy (VP8/VP9/AV1) |
| Transparency | No | Yes |
| Animation / multi-frame | Yes | Yes |
| Introduced | 2001 | 2010 |
| Developed by | MPEG (ISO) | |
| MIME type | video/mp4 | video/webm |
| Best for | sharing, uploading and playing video anywhere | web embedding and screen recordings |
What are MP4 and WebM files?
MP4 (.mp4)
MP4 is the most compatible video format today. Phones, YouTube, Facebook, WhatsApp and smart TVs all play MP4, usually with H.264 video and AAC audio.
WebM (.webm)
WebM is an open, royalty-free video format designed for the web. Browser screen recorders often save WebM, but iPhones and many editors handle MP4 better.
Tips for the best WebM results
- For phones and social media, MP4 (H.264 + AAC) is the safest choice for video and MP3 for audio.
- Very large files (over 1 GB) may exceed browser memory on phones; trim them or use a computer.
- Bookmark this page or install the app to convert MP4 files offline next time.
Private by design: how this converter works
Unlike typical online converters that upload your file to a remote server, this MP4 to WebM converter processes everything on your own device using FFmpeg compiled to WebAssembly — the same engine used by professional video tools. Your file is read into browser memory, converted, and offered back as a download — it is never sent to us.
- No upload wait — conversion starts instantly, even on slow mobile data.
- Private — safe for NID copies, certificates, bank statements and personal photos.
- No limits — no daily quota, no queue and no watermark.
- Offline-ready — once loaded, many tools keep working without internet.
Frequently asked questions
Is this MP4 to WebM converter free?
Yes — free, unlimited and without watermarks or sign-up.
Are my MP4 files uploaded to a server?
No. Conversion happens inside your browser on your own device, so your files stay private.
Will I lose quality converting MP4 to WebM?
WebM uses lossy compression, so a tiny amount of detail is discarded. At the default high quality setting the difference is practically invisible. Increase the quality slider for maximum fidelity.
Can I convert several files at once?
Yes. Drop multiple files and download them individually or together as a ZIP.
Does it work on iPhone and Android?
Yes. It works in Chrome, Safari, Edge and Firefox on phones, tablets and computers. You can also install the site as an app.
What is the difference between MP4 and WebM?
MP4 (MPEG-4 Part 14) is lossy (h.264/h.265) and best for sharing, uploading and playing video anywhere, while WebM (WebM Video) is lossy (vp8/vp9/av1) and best for web embedding and screen recordings.
Why does the first conversion take longer?
The FFmpeg WebAssembly engine (about 30 MB) is downloaded once and cached. Later conversions start immediately.