.CRX file signature
A Google Chrome extension file begins with the bytes 43 72 32 34 (Cr24 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 CRX file is still recognisable.
Signature
| Offset | Hex | ASCII |
|---|---|---|
| 0 | 43 72 32 34Followed by the format version (3) and signed header; the ZIP payload comes after. | Cr24 |
MIME type: application/x-chrome-extension · usual extensions: .crx
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.crx
file file.crxWindows (PowerShell):
Format-Hex -Path file.crx -Count 32If the bytes do not match
A file named .crx whose first bytes are something else is not a CRX 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 CRX guide explains what a genuine file should contain.