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Google Chromium patch update (.crx)

.crx file signature | application/x-chrome-package

Google Chromium patch update (CRX) is a package format created and maintained by Google for Chrome and other Chromium-based browsers. It is used to distribute browser extensions and packaged applications, allowing users to install add-ons and web app components. CRX files are generally safe, but they should be obtained from trusted sources because malicious extensions can request broad browser permissions and affect browsing privacy or security.

Safe

Magic Bytes

Offset 0
43 72 32 34

Sources: Apache Tika, Wikipedia, Gary Kessler

All Known Signatures

2 signature variants are documented for .crx files across multiple sources.

Hex Signature Offset Sources
43 72 32 34 0 Apache Tika, Wikipedia, Gary Kessler
43 72 4F 44 0 Gary Kessler

Extension

.crx

MIME Type

application/x-chrome-package

Byte Offset

0

Risk Level

Safe

Validation Code

How to validate .crx files in Python

Python 
def is_crx(file_path: str) -> bool:
    """Check if file is a valid CRX by magic bytes."""
    signature = bytes([0x43, 0x72, 0x32, 0x34])
    with open(file_path, "rb") as f:
        return f.read(4) == signature

How to validate .crx files in Node.js

Node.js 
function isCRX(buffer: Buffer): boolean {
  const signature = Buffer.from([0x43, 0x72, 0x32, 0x34]);
  return buffer.subarray(0, 4).equals(signature);
}

How to validate .crx files in Go

Go 
func IsCRX(data []byte) bool {
    signature := []byte{0x43, 0x72, 0x32, 0x34}
    if len(data) < 4 {
        return false
    }
    return bytes.Equal(data[:4], signature)
}

API Endpoint

GET /api/v1/crx
curl https://filesignature.org/api/v1/crx

See the full API documentation for all endpoints and parameters.

Frequently Asked Questions

What is a .crx file?

A .crx file is a Google Chromium patch update file. Google Chromium patch update (CRX) is a package format created and maintained by Google for Chrome and other Chromium-based browsers. It is used to distribute browser extensions and packaged applications, allowing users to install add-ons and web app components. CRX files are generally safe, but they should be obtained from trusted sources because malicious extensions can request broad browser permissions and affect browsing privacy or security.

What are the magic bytes for .crx files?

The magic bytes for Google Chromium patch update files are 43 72 32 34 at byte offset 0. These bytes uniquely identify the file format regardless of the file extension.

How do I validate a .crx file?

To validate a .crx file, read the first bytes of the file and compare them against the known magic bytes (43 72 32 34) at offset 0. This is more reliable than checking the file extension alone, as extensions can be renamed.

What is the MIME type for .crx files?

The primary MIME type for .crx files is application/x-chrome-package.

Is it safe to open .crx files?

Google Chromium patch update (.crx) files are generally safe to open. They are classified as low risk because they primarily contain data rather than executable code. However, always ensure files come from a trusted source.