Convert MP4 to WebM
The tracks are usually re-encoded, which costs a little quality. If the MP4 already carries codecs WebM accepts, they are copied as they are and nothing is lost.
They open in the converter with WebM selected.
Browse filesFiles stay on your device. Going the other way? WebM to MP4
What changes
Only if your MP4 already has AV1 or VP9 video with Opus audio does WebM accept it as it is, so the converter copies the tracks without re-encoding, in seconds and with no loss. If not, or if you change the quality, size, scale or trim, the video is decoded and compressed again, and loses a little more detail.
If it’s copied, it’s about the same size as the MP4: only the container changes. If it’s re-encoded, the size stays about the same.
When it’s worth it
Choose WebM for: Websites and browser playback. Royalty-free, and plays in every modern browser.
Stay with MP4 for: Phones, websites, social networks, and TV.
How to convert MP4 to WebM
- Drop the MP4 files on this page, or browse for them. Up to 200 at once.
- The converter opens with the files loaded and WebM selected.
- Press Convert, then save each file or all of them as a ZIP.
Questions
Does converting MP4 to WebM lose quality?
Usually a little, because the video is compressed again. Only files that already carry a codec WebM accepts are copied without loss.
What is the WebM format?
The container Google designed for the web, carrying VP8 or VP9 video with Opus or Vorbis audio. It’s royalty-free, which is why open-source projects and most browsers prefer it.
What is the MP4 format?
A container that holds a video track, one or more audio tracks and metadata, and nothing else: which codec sits inside is a separate question. H.264 or H.265 video with AAC audio is the combination almost everyone means by MP4.
Are the files uploaded?
No. The file is opened in this tab, converted here and saved from here. There’s no account and no watermark.
How many files can be converted at once?
Up to 200 per batch and about 2 GB per file, within the memory this device has available.