UniqueID or IP adress?

hi what is uniqueID it is random ID of player when join or player has still same UUID? i want to make automatic authentication but when player join only from same device so what should i use?

Unique ID in 0.12 = client ID + device ID.
It seems that it has a high chance of getting stolen and imposed (easily with mods). Check it together with IP is better.

Edit: there is also something called "secret ID" in 0.12, which will be unique for every server and very hard to fake.

i hope it

ok THX

And UUID is a string or internal?

String.

This is why it didnt save into database