UserId — the permanent key

Every Roblox account has a UserId: a number that identifies that person forever, across every game, and never changes. When your game needs to remember which player is which, this number is the answer.

#Reading a UserId

Every player has it:

local Players = game:GetService("Players")

Players.PlayerAdded:Connect(function(player)
    print(player.Name .. " has UserId " .. player.UserId)
end)

The Name is what you see ("Sam"), the UserId is the number underneath ("123456789"). Two different players can both be named "Sam" — but never the same UserId.

#Why UserId and not the name

Player names look unique, but they're a trap:

• Names can change. Someone renames, and your "Sam" record now points at a stranger.
• Names get recycled. A deleted name can be claimed by a new player.
• Two players can share a name across the migration of a nickname.

A UserId is assigned once, never changes, and is never reused. That's why it's the correct key for anything long-lived — saves, bans, leaderboards.

Players.PlayerAdded:Connect(function(player)
-- your print here
end)