Charles checks for updates everytime you start Charles. You will be alerted if there is a new version available. You can also manually check for updates in the Help menu.

Automatic Update Checking can be turned off in the Preferences. You can also manually request an update check in the Help Menu.

The automatic update check makes a request to http://xk72.com/charles/latest.php passing a single parameter, v, containing your current version of Charles. No personal or identifying information is sent. The server responds with the version number of the latest version or nothing if you’re current.