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 3.10.1. Read the Release Notes.
You'll need to install a new Charles SSL Root Certificate to continue using SSL Proxying. See SSL Proxying in the Help menu in Charles for steps to install on various platforms.
Mac OS X users
The main download of Charles now includes Java 8, so you no longer need to use the alternative download for better SSL support. The alternative download is now strictly for oldies.
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.