Intro to Command Blocks
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Command Blocks are special blocks in Minecraft. The same commands (cheats) you type in chat can be run automatically using command blocks and it can be reused without needing to type all over again.
They can only be placed or destroyed by a player with the Operator permission level in gamemode Creative.
- Open your world settings.
- Under Cheats, toggle "Activate Cheats" setting ON.
/give @s command_blockcommand in chat.
Command Block UI
Command Block Types
Impulse runs the command once each time it is powered.
Chain runs the command in a sequence, ie. only after the previous command block it is connecting from was run.
Repeat runs the command every game tick. There are approximately 20 ticks per second. A delay can be applied to adjust how often the command is executed, explained below.
Command Block Conditions
Conditional command blocks will run the command only if the previous command block it was connecting from had an output that was
Conditional command block states are shown by a small indent into the command block's texture, as shown below:
- Impulse Conditional Command Block
- Chain Conditional Command Block
- Repeating Conditional Command Block
Unconditional command blocks will run the command regardless. Whether the previous command block it was connecting from had an output that was
false (failed) or even if it came with a syntax error the command block will still run the command.
Command Block Redstone States
Needs Redstone command block can only be activated with redstone power. Using buttons, levers, redstone torch etc..
Always Active command block will be activated as soon as you close the command block UI.
Command Block Tick Delay
In this option you may specify how much delay you want there to be before the command block runs the command.
The ticks refer to Minecraft game ticks. A tick is simply a unit of measure for time in games. 1 second in real life is approximately 20 game ticks in Minecraft.
Command Block Hover Note
This option allows you to put a hovering text on your command blocks. It's useful for giving short-names for easy identification when working with many command blocks.
When a command is run, the hover note will be displayed with the output in chat if gamerule
commandblockoutput is enabled.
The paste button allows you to paste commands from your clipboard to the 'Command Input' box.
Command Block Output
Toggle the 'Previous Output' button in the command block UI to see command output and block details.
/you type before the whole command is not required in a command block but doing so won't cause any errors.
A redstone comparator can read command blocks outputs. If output is true, it will send anywhere from 1 to 15 redstone signals depending on the output value.
You can check if a command output is
falseby running it in chat. A red output will be a
falseoutput or a syntax error. A white output means command was run successfully.
You can also tell if a command was
falseby checking whether action was performed or not.
An output with a value of
0is usually a false output.
Disabling Command Messages In Chat
Run in Chat:
/gamerule commandblockoutput falseto disable command block messages in chat.
/gamerule sendcommandfeedback falseto disable feedback from commands entered in chat.
Command Block Placement
When placing command blocks in a line (arranged to work together) for any system, make sure the consecutive command blocks connect/start from the head of the arrow.
The arrow/facing direction can be observed from the command block texture.
✅ Correct Placement
❌ Incorrect Placement
Troubleshooting Command Blocks
In world settings, under Cheats, make sure command blocks have not been disabled.
Make sure gamerule
maxcommandchainlengthis not set to 0
Make sure there are no unwanted redstone power that is interfering with the command block. It can be from redstone dust, lever, redstone torch etc..
Try switching between Always Active & Needs Redstone.
Double check the block type, condition & the command syntax. Check 'Previous Output' after powering it once again.
Just like redstone, command blocks must also be in loaded chunks for them to work. You can use a tickingarea to keep them loaded when players are not nearby. Refer to /tickingarea command documentation for more info.
If nothing seems to work simply break and place that command block again.
What you have learned
What you have learned:
- How to obtain a command block in game.
- How the different types of command blocks behave and what they look like.
- What the different command block options are (including conditional, state and delay.)
- How command blocks output data by redstone and chat messages.
- How to properly place command block chains.
- How to resolve 'command block not working'
To put what you have learned into practice, try making this simple Entity Counter system.
Note: when setting up command block systems, always the first command will be
Unconditional Always Activeand the rest will be
Unconditional Always Active(all 0 ticks delay) unless specified otherwise.
(Recommended) Read Next: Understanding Selectors