Re-encode video to WebM with VP9 video and Opus audio — smaller files at the same quality, ideal for embedding on the web.
MP4 · MOV · WebM · MKV · AVI · GIF
WebM pairs the VP9 video codec with Opus audio, both royalty-free and both more efficient than the MP4 equivalents. For a background loop, a product demo or a documentation clip, the same perceived quality arrives in noticeably fewer bytes.
The safest pattern is still to offer WebM first and MP4 as the fallback:
<video><source src="clip.webm" type="video/webm"><source src="clip.mp4" type="video/mp4"></video>
Browsers pick the first source they can play, so modern clients get the smaller file and older ones still work.
VP9 in a browser sandbox is slow — expect several seconds of processing per second of video. If you need speed more than size, H.264 compression encodes far faster at a modest size penalty.
At the same visual quality, VP9 in WebM is typically 25–35% smaller than H.264 in MP4. The trade is encoding time — VP9 is considerably slower to encode.
Every current desktop and Android browser does, and Safari has supported VP9 since 2021. For maximum reach, ship both and let the browser pick with two <source> tags.
VP9 is computationally expensive, and this runs single-threaded inside a browser sandbox. Short clips are fine; for long videos, a desktop encoder will be far quicker.
No. Encoding happens locally in WebAssembly — the file never leaves your device.
Yes. The browser keeps the input and working data inside the tab, and WebAssembly does not have access to hardware video encoders. Use a desktop encoder for long or high-resolution footage when speed and memory use matter.