CRX (Chrome Extension) file format

.crx · package (signed ZIP) · introduced 2010 by Google

What is a CRX (Chrome Extension) file?

CRX is the package format for Chrome and Chromium-based browser extensions. It is a standard ZIP file prefixed with a "Cr24" magic header and a developer signature. Stripping the header yields a regular ZIP that any archiver can open.

Most readers reach this page after double-clicking a .crx file and finding their operating system unsure what to do with it. The good news: CRX (Chrome Extension) is a well-understood format with mature tooling on every major platform. It is supported in one click by mainstream archivers on Windows, macOS, and Linux.

How to extract a CRX (Chrome Extension) file

Opening a .crx file is straightforward on every modern operating system. The exact steps depend on which platform you are on:

On Windows

Locate the .crx file in File Explorer.
Right-click the file. If you have 7-Zip installed, choose 7-Zip → Extract Here. On Windows 11 the built-in extractor handles ZIP, 7z, RAR and several other formats directly through Extract All…
If prompted, pick a destination folder and click Extract.
The extracted files appear in a folder next to the original archive.

On macOS

Find the .crx file in Finder.
Install The Unarchiver from the Mac App Store, or Keka for both creating and extracting.
Right-click the file → Open With → The Unarchiver (or just double-click after Unarchiver is set as the default).
The extracted folder appears next to the archive.

On Linux

Use your file manager: right-click the archive → Extract Here (file-roller on GNOME, Ark on KDE).

On the command line, run one of:

7z x archive.crx    # works for almost any format

The files appear in the current directory.

How to create a CRX (Chrome Extension) file

To pack files into a .crx archive, you typically need an archiver that supports writing this format. Not every tool can create every format — for example, only WinRAR can create real RAR files. The sidebar lists the software known to read and write CRX (Chrome Extension).

On the command line, the canonical create command is:

# Use 7-Zip, PeaZip, or the format's reference tool to create .crx files.

If you regularly create archives at scale, a dedicated archive automation suite can wrap this command in scheduled jobs, integrity checks, and offsite replication.

Strengths

Cryptographic publisher signature
Just ZIP underneath

Weaknesses and limitations

Browser-specific
Sideloading restricted by Google policy

Typical use cases

Chrome Web Store extensions
Enterprise extension distribution

Technical details

CRX (Chrome Extension) uses the ZIP + signature header algorithm and is identified on disk by the magic byte sequence Cr24. The standard MIME type is application/x-chrome-extension. The format is an open specification and is free for any use.

Frequently asked questions

Is CRX (Chrome Extension) safe to open?

Archive files are containers — they are only as safe as what they contain. A .crx from a trusted source is fine; one received from a stranger can hold malicious executables, scripts, or files engineered to exploit bugs in your archiver. Always keep your archiver updated, and never run unknown executables that come out of an archive. A safe workflow is to extract into a sandbox and scan the contents before opening anything.

What is the maximum file size?

Modern ZIP-based formats use the ZIP64 extension to support archives larger than 4 GB and individual files larger than 4 GB, up to 16 EB in theory. Older tooling that does not understand ZIP64 will report a corruption error on such files.

Can I password-protect a CRX (Chrome Extension)?

Some archivers can wrap CRX (Chrome Extension) files in an encrypted container, but the format itself does not always include built-in encryption. Check your archiver's documentation.

How does CRX (Chrome Extension) compare to other formats?

See our format comparison pages such as ZIP vs 7z, ZIP vs RAR, and tar.gz vs tar.xz for side-by-side feature tables.