Updated:
1. Diamond under your feet
/execute as @a at @s if block ~ ~-1 ~ grass_block run setblock ~ ~-1 ~ diamond_blockPut it in a repeating, always active command block. The if block check limits it to grass, so floors stay safe.
2. Change a 3x3 area
/execute at @a run fill ~-1 ~-1 ~-1 ~1 ~-1 ~1 gold_block replace grass_block3. Ice path on water
/execute at @a run fill ~-2 ~-1 ~-2 ~2 ~-1 ~2 frosted_ice replace waterFrosted ice melts back to water over time. Use ice to keep it.
4. Flowers behind you
/execute as @a at @s if block ~ ~-1 ~ grass_block run setblock ~ ~ ~ poppy keepkeep only places the flower in air.
5. Undo
/fill ~-20 ~-3 ~-20 ~20 ~3 ~20 grass_block replace diamond_blockStop the command block first. See the fill command.
6. Particle trail
/execute at @a run particle minecraft:heart ~ ~ ~ 0.2 0.2 0.2 0 2Leaves hearts behind without changing any blocks. On Bedrock use particle minecraft:heart_particle ~ ~ ~.
7. Only for chosen players
/tag Steve add trail
/execute as @a[tag=trail] at @s if block ~ ~-1 ~ grass_block run setblock ~ ~-1 ~ diamond_blockTag a player first, then use @a[tag=trail] in the repeating block. Remove it with /tag Steve remove trail. See the tag command.
8. Only while holding an item (Java)
/execute as @a at @s if items entity @s weapon.mainhand minecraft:blaze_rod if block ~ ~-1 ~ grass_block run setblock ~ ~-1 ~ diamond_blockThe path appears only while the player holds a blaze rod, like a magic wand (1.20.5+). See held item effects.
Troubleshooting
- Changes only once: set the block to Repeat and Always Active.
- Nothing while jumping: the block below is air; that is normal.
- Lag: keep fill areas small on busy servers.
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