There are two ways to make a Minecraft server allow list only. The first is through the chat box in-game, using the command "/allowlist on" (Bedrock edition) or "/whitelist on" (Java edition) and then "/allowlist add username" or "/whitelist add username" depending on which edition. The other way is to make a whitelist.json file at the root of your server, and add the username and UUID of a player to the file. //

This is one step that I forget far more often than I'd like to admit. Becoming an op on your server is crucial. With op powers, you can do just about anything in the Minecraft world.

To make yourself an op, simply type "/op username" in-game, or edit the ops.json file at the root of your Minecraft server.