.WEBM file signature
A WebM media file file begins with the bytes 1A 45 DF A3 at the start of the file. The signature is the same whatever the file is named, which is why a renamed or extensionless WEBM file is still recognisable.
Signature
| Offset | Hex | ASCII |
|---|---|---|
| 0 | 1A 45 DF A3EBML header with DocType webm. |
MIME type: video/webm · usual extensions: .webm
How to check a file's signature
Without installing anything: drop the file on our detector. It reads the bytes in your browser and shows the hex dump alongside the verdict; nothing is uploaded.
macOS and Linux (Terminal):
xxd -l 32 file.webm
file file.webmWindows (PowerShell):
Format-Hex -Path file.webm -Count 32If the bytes do not match
A file named .webm whose first bytes are something else is not a WEBM file. The common explanations are a wrong or deliberately misleading extension, a download that saved an HTML error page instead of the file, or a container such as ZIP wrapping the real content. The detector reports what the bytes say; the WEBM guide explains what a genuine file should contain.