Quick verdict
MP4 for maximum compatibility (every device, every social platform, every editor). WEBM when your audience is web-only and you want smaller files on modern browsers.
MP4 and WEBM are both modern web video containers. The practical difference is the codec inside: MP4 typically holds H.264, and WEBM holds VP8 or VP9 (and sometimes AV1).
WEBM is Google's open-source-friendly format, originally designed to give the web a royalty-free codec. MP4 uses H.264, which is patent-encumbered but has hardware acceleration on virtually every device shipped in the last 15 years.
For most users, MP4 is the safe default. WEBM is the better choice when you control the playback environment (a modern browser) and care about file size or licensing.
| Feature | MP4 | WEBM |
|---|---|---|
| Typical codec | H.264 | VP8 / VP9 / AV1 |
| Hardware acceleration | Yes (everywhere) | Partial (newer devices) |
| File size (same quality) | Baseline | 20–40% smaller (VP9) |
| Browser support | 100% | 95%+ |
| iOS / Safari | Yes | Partial |
| Social media upload | Always accepted | Often re-encoded |
| Editing software | All | Web-focused tools |
| Licensing | Patent-encumbered (H.264) | Royalty-free |
Use MP4 when
- You're uploading to social media or a CDN that may transcode.
- You need playback on iOS / older Safari without surprises.
- You're sharing with non-technical users.
- You care about battery life on mobile (H.264 has hardware decoding).
Use WEBM when
- You're embedding video on your own website and audience is modern browsers.
- You care about file size — VP9 typically saves 20–40% vs H.264.
- You're building an open-source project and want a royalty-free codec.
- You're distributing short loops (hero video, animated background) where size matters.
Convert between MP4 and WEBM in your browser
FAQ
- Does WEBM work on iPhones?
- Partially. Safari on iOS 16+ supports WEBM (VP8/VP9), but older iPhones do not. Provide both WEBM and MP4 sources in a <video> tag for safest playback.
- Is WEBM smaller than MP4?
- Usually yes. WEBM with VP9 is typically 20–40% smaller than H.264 MP4 at the same visual quality. AV1 in WEBM is even smaller but slower to encode and decode.
- Why does my WEBM upload fail on Instagram / TikTok?
- Social platforms standardize on MP4 (H.264). Convert your video to MP4 before upload — they will re-encode anyway, but accepting your MP4 reduces processing time and reduces quality loss.
- Why is converting MP4 to WEBM so slow?
- WEBM encoding (VP8/VP9) is computationally heavier than H.264. In the browser, single-threaded ffmpeg.wasm makes this slower still. Expect ~5–10× real time on mid-range hardware.