This tutorial assumes you are already logged in to your admin control panel.
Joomla uses session lengths to automatically log out users that have been inactive for a set amount of time; the default is 15 minutes. Let's see how to change this.
1) Click Site.
2) Then Global Configuration.
3) Go to the System settings.
Scroll down and right.
4) Change the number of minutes next to Session Lifetime.
5) Click Save.
The session will now last an hour and a half before expiring.
That's it! You now know how to change the session lifetime in Joomla.