How to enable command blocks on a Minecraft server

Your version is in the Minecraft version field on the Settings tab. On a world created on 1.21.9 or newer, command blocks work without changing anything. If the game still says command blocks are not enabled on such a server, the game rule is set to false.

The Command blocks switch under Settings writes the enable-command-block line. Minecraft 1.21.9 and newer no longer read that line, so on those versions the game rule decides and the switch has no effect.

1. Start the server. Game rules can only be read and changed while it runs.
2. Open the Console tab.
3. Type gamerule command_blocks_work and press Send. The console answers with the current value, for example Gamerule command_blocks_work is currently set to: false.
4. Type gamerule command_blocks_work true and press Send. The change works at once, without a restart.

On 1.21.9 and 1.21.10 the rule has its older name: gamerule commandBlocksEnabled true. Each version only accepts its own name, so the other one gives an error. Keep inventory and game rules lists the old and new names of the other rules.

Command blocks in the Nether and the End on Paper

Paper and Purpur keep separate game rules for each world, and a gamerule typed in the console only changes the overworld. For command blocks in the Nether or the End, also send these two lines:

execute in minecraft:the_nether run gamerule command_blocks_work true
execute in minecraft:the_end run gamerule command_blocks_work true

On other server types the two extra lines do no harm.

1. Open Settings and go to Server settings.
2. Under Gameplay, turn on Command blocks. Typing command in Search settings finds it.
3. Press Save changes.
4. Restart the server. Minecraft reads server.properties only when it starts.

To change the file by hand, open Files, click server.properties in the top folder and set the line to enable-command-block=true. Use lower case and no spaces around the equals sign, then restart. What the other lines in that file do is in server.properties explained.

Before you can place a command block, your account needs two things:

• Operator status of level 2 or higher. Open Players, choose Operators and press Add operator, or type op and your name in the console.
• Creative mode. Type /gamemode creative in the game. In survival you can hold a command block, but you cannot place, open or break it.

Then type one of these commands in the game chat:

@s stands for the player who types the command, so it only works in the game. In the console, use your Minecraft name: give Steve minecraft:command_block.

Operators can also turn on Operator Items Tab in the game options under Controls. The creative inventory then shows an Operator Utilities tab that holds all command blocks.

Placing and editing command blocks needs operator level 2. A new operator gets the level set in op-permission-level in server.properties, which is 4 by default. This only matters when someone lowered it. The line is not in the Settings form; change it in the Files tab and restart.

A command block runs its own command at level 2. Commands that need level 3 or 4, such as op, ban, whitelist and stop, fail inside a command block. How to give one operator a different level is in whitelist and operator levels.

Right click a placed command block to open its screen. Type the command in the Console Command field and press Done. A slash in front of the command is optional. The chat confirms it with Command set: followed by the command.

The buttons in the command block screen

• Impulse, Chain or Repeat sets the type. Each click switches to the next one.
• Unconditional or Conditional: a conditional block only runs when the block pointing into it succeeded on its last run.
• Needs Redstone or Always Active: whether the block waits for a redstone signal.
• Previous Output shows the result of the last run, which is the quickest way to find a typo.

The arrows on the sides of a command block show which way it points. A chain block only runs when the block before it points straight into it, so build a chain in the direction of the arrows.

Some problems show no message at all:

• Right click does nothing. You are in survival or adventure, or your operator level is below 2.
• The block runs once and then stops. It is an impulse block. Set it to Repeat for a command that has to keep running.
• Blocks in the Nether or the End stay silent on Paper. The game rule is off in that world; send the two execute in lines from the game rule section.
• A change in server.properties did nothing. The server was not restarted, or it runs 1.21.9 or newer, where that line is no longer read.

When a command block runs a command such as give, tp or gamemode, operators get a line about it in chat and the console log gets one too. A repeat block that runs such a command produces 20 of those lines a second. These game rules control that:

gamerule command_block_output false

Set command_block_output to false once your build works, so the chat stays readable for players and staff.

A repeat block set to Always Active runs 20 times a second for as long as its chunk is loaded. A command that searches every entity, such as kill @e[type=minecraft:item], costs tick time on every run.

• Narrow the selector. @e[type=minecraft:item,distance=..20] only looks within 20 blocks of the command block.
• Check first, then act. Put execute if entity @a[distance=..30] in the repeat block and the real work in conditional chain blocks behind it, so the work only happens when a player is near.
• Move large systems into a data pack. A function in the minecraft:tick tag runs every tick like a repeat block, and you edit it as a text file. See install datapacks.

When a command block lags the server or loops something harmful, gamerule command_blocks_work false stops every command block at once. Find the block, fix the command and switch the rule back on. Reduce lag shows how to measure what costs tick time.

Make a backup in the Backups tab before you test commands such as fill, clear or kill in a repeat block. A wrong selector runs 20 times a second, and commands have no undo.

Only operators of level 2 or higher in creative can place, edit or break command blocks. Other players can still trigger them with a button, lever or pressure plate, which is how maps let players use them without any rights.

• A command block keeps running after the operator who set it up goes offline or loses operator status. Check what their blocks do before you take someone's rights away.
• Turn command blocks off when your server does not use them.
• For staff who need a few commands and no command blocks, use a permissions plugin. Permissions with LuckPerms sets that up command by command.
• For the commands themselves, Minecraft server commands lists the ones admins use most, with examples.