Click the green flag to see your userID! If you are not signed in your userID will return as 0.
The userID block was a block that was originally going to be added in Scratch 2.0, but later removed in beta. It was like the username block, but it detected what # viewer you were, so for example if you were the 5th person to view the project, your userID would be 5. You can read more about it here: https://en.scratch-wiki.info/wiki/User_ID_(block)
