Convert MP4 to WebM
Lighten videos embedded on web pages. VP9 is 20–30% smaller than H.264 at the same quality.
Settings
How to use
- 1
Add videos
Drop MP4, MOV, WebM, MKV and similar files. Several videos can be converted in turn with the same settings.
- 2
Choose the output format
MP4 (H.264), WebM (VP9), MOV or MKV. When the codec already matches, the stream is copied instead of re-encoded, which is very fast.
- 3
Convert and save
Save once the progress bar reaches 100%. Long videos take a while; keep the tab open.
When to use WebM
WebM plays in all major browsers and is smaller than H.264 MP4 at the same quality — well suited to background videos and previews on web pages. It can also carry transparency.
The iPhone Photos app, most video editors and TVs cannot play it, though. Keep MP4 for distribution outside the web.
Frequently asked questions
Is quality lost?
It is re-encoded, so it changes slightly according to the Quality setting.
Conversion is slow
VP9 encoding is more demanding than H.264, and on devices without a hardware encoder it can take about as long as the video itself.
Does it play in Safari?
Yes, in Safari 14 and later, and on iOS from Safari 15.
What happens to the audio?
It is converted to Opus, which sounds better than AAC at the same bitrate for both music and speech.
Help us improve the service
If a conversion fails, sending us the circumstances helps us track down the cause. Knowing which devices and formats fail most often, and how long processing takes, lets us revise the supported formats and fix the bugs behind them. If you don't mind, leaving this on is a real help.
What is sent
The tool you used and the settings you chose (output format, quality, etc.), your device specs (GPU, memory, core count), the input format with a rough size, how many files succeeded or failed and how long it took, and the error type and details when something fails.
What is never sent
The files themselves, file names, text, subtitles or prompts you add to a video, and IP addresses. The data goes only to this site's own server, never to a third-party service.