From the Backend:
- Log in the backend of your website,
- Go to System → System Information: this screen contains all system information you may need, the Joomla! Version currently running, and also PHP, database versions and so on.
The Joomla! version is also mentioned at the bottom right of every pages of the backend.
If you don’t have access to the backend, you can find the Joomla! version by FTP:
- Go to root → librairies → cms → version → version.php: the version is mentioned in the lines public $RELEASE (for the release version) and public $DEV_LEVEL (for the maintenance version).