Players

Who may join an instance, who is kept out, and who holds server commands are all declared in the players section of mc.kdl and written to the server when the instance starts:

players {
    allow {
        Notch
        jeb_
    }

    ban {
        Griefer reason="stole the beacon" created="2026-09-06T14:00:00Z"
    }

    op {
        Notch level=4
    }
}

See The Manifest Format for every key. The allow list is enabled by default; to open the instance to everyone, set allow-list #false in the server section. Operators may join regardless of the allow list.

Editing the lists

mc allow, mc ban, and mc op edit the section for you. Each has add, remove, and list subcommands:

mc allow add Notch jeb_
mc ban add Griefer --reason "stole the beacon" --for 7d
mc op add Notch
mc op list

Names are looked up when added, so a typo fails at the command rather than at the next start, and the account’s own casing is recorded. Names are matched regardless of case afterwards.

How the lists reach the server

The server keeps its lists in JSON files inside instance/. mc regenerates them from the manifest on every start, so the manifest is the single source of truth and those files are never edited by hand. Each player’s identity is resolved once and remembered in mc.lock, so a start never waits on a lookup.

When the instance is running and its remote console is reachable, a command also applies the change to it right away, so a newly banned player is disconnected and a newly allowed one can join without a restart. The remote console is reachable when an RCON password is configured — see Environment Variables. Two kinds of change cannot be applied live and wait for the next restart: an operator level or player limit bypass, and a ban expiry. The command says so with a warning.

Changes made from inside the game, such as /ban or /op typed by an operator, live only in the server’s files and are replaced by the manifest at the next start. Put them in the manifest with the matching mc command to keep them.

Offline mode

An instance with online-mode #false in the server section does not verify accounts, and the server identifies players by name alone. mc derives the identity the server expects from the name, so no lookup happens and any name is accepted.