.JP2 file signature
A jpeg2000 file begins with the bytes 00 00 00 0C 6A 50 20 20 0D 0A 87 0A (....jP .... in ASCII) at the start of the file. The signature is the same whatever the file is named, which is why a renamed or extensionless JP2 file is still recognisable.
Signature
| Offset | Hex | ASCII |
|---|---|---|
| 0 | 00 00 00 0C 6A 50 20 20 0D 0A 87 0A | ....jP .... |
MIME type: image/jp2 · usual extensions: .jp2
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.jp2
file file.jp2Windows (PowerShell):
Format-Hex -Path file.jp2 -Count 32If the bytes do not match
A file named .jp2 whose first bytes are something else is not a JP2 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 JP2 guide explains what a genuine file should contain.