Hello, I am creating a custom GUI for my plugin and I was wondering what is the best way to check if a player is in our GUI or not. I had the idea of checking the name but 2 problems come: It may interfeer with other plugin, if two have the same name then RIP The name can be changed in the config, so if the user deside to refresh the config, changing the name, if a user have the GUI oppened then it will break. So I have been looking in the internet to find a good solution. What I found is this: https://www.spigotmc.org/threads/qu...r-is-interacting-with-your-custom-gui.225871/ Which I thought was a very good way of doing it, because it is safe. Then I tried to know what was the InventoryHolder interface (nobody should use something that he don't undestand I guess ^^). So I found this post: https://www.spigotmc.org/threads/what-is-the-inventoryholder-interface.342812/ Which complety discourage the method told in the first link given. So I am a little bit confused about what to do for my GUI. Oh and in the tutorial I used: https://www.spigotmc.org/wiki/creating-a-gui-inventory/ they compare the Inventory object, which is not possible in my case because every player will have a different GUI menu.