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How to unpack a packed chrome theme(*.crx)? Their FAQ states how to pack, but not how to unpack.

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5 Answers

I got the solution: apparently, a .crx file is just a renamed .zip file. Additionally, when you install it, the theme is decompressed into the chrome install directory...

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Not quite; it’s not just a renamed ZIP. Open one in a hex-editor and see that there is clearly a proprietary header. That said, yes, it is basically a ZIP, and can be opened in most ZIP-capable programs. I prefer 7-Zip. –  Synetech Jul 13 '11 at 3:25
    
@Synetech is correct, the file header contains a public key and signature. Google's .crx Package Format page explains this. In practice, you should be able to extract a .crx file with unzip, and it will ignore the extra bytes. If you do end up needing to chop off the header first, running unzip -l will show you how many (N+1 bytes with tail). For example: If unzip -l complains with warning [file.crx]: **306 extra bytes at beginning or within zipfile**, then run: tail -c +307 file.crx > /tmp/file.crx; unzip -l /tmp/file.crx –  TrinitronX Dec 13 '12 at 22:45
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Actually it's more than a zip. When you unzip -l you'll see a message:

warning [extension.crx]: 306 extra bytes at beginning or within zipfile

So the crx file is 306 bytes of something plus a zip archive.

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This video explains everything about what a .crx is. In addition to a .zip holding all the extension's resources, it includes a public key and a signature, to ensure integrity and authenticity of the file: Antony Sargent explains .crx files Hosted by: youtube.com

The details of the .crx package format are published here.

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Chrome extension install directory:

Mac:

/Users/username/Library/Application Support/Google/Chrome/Default/Extensions

Windows 7:

C:\Users\username\AppData\Local\Google\Chrome\User Data\Default\Extensions

Windows XP:

C:\Documents and Settings\YourUserName\Local Settings\Application Data\Google\Chrome\User Data\Default
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Best solution out of them all. This worked for me, none of the others did. –  daviesgeek Jan 27 '12 at 17:20
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Yep aviraldg is right. rename it to a .zip and use your favorite extraction tool. XPIs for firefox, etc, are the same process.

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