Minecraft wiki entry for Command_Block, associated text: Chat: The output message is written to the chat text in singleplayer mode, or broadcast to all other ops in multiplayer mode, unless it has been suppressed with /gamerule commandBlockOutput false. Some commands may write additional text to the chat as their normal function, which won't be suppressed (for example, the /say command writes a message to the chat of all players), separate from the output message. Chat messages that would usually be prefaced by a player's name (such as from the /me, /say and /tell commands) use @ ‌[Java Edition only] / ! ‌[Bedrock Edition only] as the player name. If the command block had been named in an anvil before placement, that name is used instead. In Bedrock Edition, it can also modified in the GUI.