This page describes how to package your extension. As the Overview explains, extensions are packaged as signed ZIP files with the file extension "crx" — for example, myextension.crx.

Note: You might not need to package your extension. If you publish your extension using the Chrome Developer Dashboard, then the only reason to create your own .crx file would be to distribute a non-public version — for example, to alpha testers.

When you package an extension, the extension is assigned a unique key pair. The public key is used as the identifier for the extension. The private key is kept private and used to sign each version of the extension.

Creating a package

To package an extension:

1. Bring up the Extensions management page by going to this URL:

   chrome://extensions

2. If Developer mode has a + by it, click the +.
3. Click the Pack extension button. A dialog appears.
4. In the Extension root directory field, specify the path to the extension's folder — for example, c:\myext. (Ignore the other field; you don't specify a private key file the first time you package a particular extension.)
5. Click OK. The packager creates two files: a .crx file, which is the actual extension that can be installed, and a .pem file, which contains the private key.

Do not lose the private key! Keep the .pem file secret and in a safe place. You'll need it later if you want to do any of the following:

• Update the extension
• Upload the extension using the Chrome Developer Dashboard

If the extension is successfully packaged, you'll see a dialog like this that tells you where to find the .crx and .pem files:

Updating a package

To create an updated version of your extension:

1. Increase the version number in manifest.json.
2. Bring up the Extensions management page by going to this URL: chrome://extensions
3. Click the Pack extension button. A dialog appears.
4. In the Extension root directory field, specify the path to the extension's folder — for example, c:\myext.
5. In the Private key file field, specify the location of the already generated .pem file for this extension — for example, c:\myext.pem.
6. Click OK.

If the updated extension is successfully packaged, you'll see a dialog like this:

Packaging at the command line

Another way to package extensions is by invoking chrome.exe at the command line. Use the --pack-extension flag to specify the location of the extension's folder. Use --pack-extension-key to specify the location of the extension's private key file. For example:

chrome.exe --pack-extension=c:\myext --pack-extension-key=c:\myext.pem

To suppress the dialog, add --no-message-box to the command.

Package format and scripts

For more information on the format, as well as pointers to scripts you can use to create .crx files, see CRX package format.