.webm — WebM Video
Video video/webm
What a .webm file is
An open, royalty-free container for VP8/VP9 or AV1 video with Vorbis or Opus audio, designed for HTML5 video.
How to open it
All current browsers, VLC, MPV.
Worth knowing
Smaller than MP4 at equivalent quality, but Safari support arrived late and some older devices still struggle.
How to identify a .webm file
A file's extension is only its name — renaming a.png to a.webm changes nothing inside. What software actually reads is the magic number, the first few bytes of the file.
| Signature | 1A 45 DF A3 |
| MIME type | video/webm |
| Category | Video |
Identical EBML header to MKV; the difference is which codecs are allowed inside.
# what is this file really?
file mystery.webm
# look at the first bytes yourself
xxd mystery.webm | head -2
head -c 16 mystery.webm | xxd
# Windows PowerShell
Get-Content mystery.webm -AsByteStream -TotalCount 16 | Format-HexFrequently asked questions
What is a .webm file?
An open, royalty-free container for VP8/VP9 or AV1 video with Vorbis or Opus audio, designed for HTML5 video.
How do I open a .webm file?
All current browsers, VLC, MPV.
Is .webm safe to open?
Yes. A .webm file is data, not code — opening one cannot execute anything by itself.
Can I change a file's extension to convert it?
No. Renaming changes the label, not the bytes. The one place it appears to work is between formats that genuinely share a container — renaming .docx to .zip works because a DOCX is a ZIP. Everything else needs a real converter.