Download the latest version of Charles below. Version 3.X of Charles is a free upgrade for all registered users.
The latest version of Charles is 3.9.3. Read the Release Notes.
Mac OS X users note: Improved SSL support is only available on the Oracle Java version of Charles, which is the alternative download for Mac OS X.
Mozilla Firefox add-on
Charles requires an add-on in Firefox to autoconfigure Firefox's proxy settings. Charles will automatically prompt you to install the add-on when you run Charles. If the add-on is not automatically installed, you can manually activate Mozilla Firefox Proxy in the Proxy menu. Alternatively you can download and install the add-on manually.