The AEM default login relies on tokens that are stored on the client side, that's why you can log in in 2 separate browsers with the same users at the same time.
If you need to change this behavior to allow a user to log in just once, you would have to create a custom Authentication Handler which will check if the user is already with a session open. To check if the session is opened, you can use something like this: https://www.aemtutorial.info/2021/11/generate-reports-for-users-last-log-in.html
The AEM default login relies on tokens that are stored on the client side, that's why you can log in in 2 separate browsers with the same users at the same time.
If you need to change this behavior to allow a user to log in just once, you would have to create a custom Authentication Handler which will check if the user is already with a session open. To check if the session is opened, you can use something like this: https://www.aemtutorial.info/2021/11/generate-reports-for-users-last-log-in.html