Is WebM actually smaller than MP4?

VP9 WebM is typically 20–40% smaller than H.264 MP4 at the same perceptual quality. For video-heavy websites, this can be significant — a 10 MB MP4 background video might become a 6 MB WebM. AV1 WebM is even more efficient but encoding is extremely slow in software, so we use VP9.

Does Safari support WebM?

Safari on macOS 12.3+ and iOS 16+ added basic WebM support, but it's incomplete (VP8 only, not VP9). For universal compatibility, always provide an MP4 fallback. Use the HTML5 element with two tags: WebM first (for Chrome/Firefox), MP4 second (for Safari).

How long does VP9 encoding take compared to H.264?

VP9 encoding is 3–5× slower than H.264 at comparable quality. A 1-minute MP4 that takes 30 seconds to re-encode as H.264 might take 2–3 minutes as VP9. This is inherent to the VP9 codec — it's a deliberate trade-off for better compression. AV1 is even slower. For large files, consider using a desktop tool like Handbrake.

Can I use the WebM output as a video background on my website?

Yes. Short WebM loops are ideal for web backgrounds — they load faster than MP4 equivalents. Use `autoplay muted loop playsinline` attributes on the ` ` element. For cross-browser support, pair with an MP4: ` `.

What audio codec does the WebM output use?

Opus audio at 128 kbps. Opus is the preferred audio codec for WebM — it outperforms Vorbis and is royalty-free. All browsers that support VP9 also support Opus, so there are no compatibility issues.

Convert MP4 to WebM — Optimized for the Web

WebM with VP9 encoding produces smaller files than H.264 MP4 at equivalent quality — making it ideal for web delivery. The HTML5 `<video>` element supports WebM in all modern browsers. If you're serving video on a website, WebM as a primary source with MP4 fallback is the recommended approach. Convert your MP4 clips to WebM here, in your browser, with no upload needed.

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Up to 500.0 MB per file

How to use this tool

Upload your MP4 file
Drop an MP4 video file. Up to 500 MB supported. Note that VP9 encoding is computationally intensive — allow extra time for larger files.
Let FFmpeg encode
FFmpeg uses VP9 (libvpx-vp9) with CRF 30 and Opus audio. VP9 encoding is slower than H.264 but produces 20–40% smaller files at the same quality. Progress is shown in real time.
Download the WebM
The output WebM file is ready for web delivery. Use it as the primary `<source type="video/webm">` in an HTML `<video>` element, with an MP4 fallback for Safari.
Deploy to your website
WebM plays in Chrome, Firefox, and Edge. Use a `<picture>`-style approach with `<source>` elements to serve WebM to modern browsers and MP4 to Safari.

Frequently asked questions

Convert WebM to MP4 Convert MOV to MP4 Convert MKV to MP4 Convert MP4 to GIF Mute Video Extract Audio from Video

Convert MP4 to WebM — Optimized for the Web

How to use this tool

Frequently asked questions

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