Red POW Block

Red POW Blocks are a variant of POW Block that, much like the blue type, causes an earthquake effect onscreen. However, these do not drop any coins and their effects are shorter-ranged; instead, they break and hit blocks and can start chain reactions if another Red POW Block is in range of the effect.

There have been instances of regular POW Blocks being colored red in some games, such as Super Mario Bros. 2. However, these do not behave as Red POW Blocks do.

New Super Mario Bros. 2
Red POW Blocks first appear in New Super Mario Bros. 2; they are the only POW Block type in the game. They cannot be picked up, so they must be activated by hitting them normally. While they cannot defeat on-screen enemies out of its range or drop midair coins, their tremors can hit nearby blocks; they can start a chain reaction with other nearby Red POW Blocks when activated.

Super Mario 3D World / Super Mario 3D World + Bowser's Fury
Red POW Blocks reappear in Super Mario 3D World and its Nintendo Switch port, which marks their first appearance in a 3D Super Mario platformer. They act like they did in New Super Mario Bros. 2, though they can also reveal the locations of Hidden Blocks.

Super Mario Maker 2
Red POW Blocks reappear in Super Mario Maker 2, albeit only in the Super Mario 3D World style and instead behaving like they did in New Super Mario Bros. 2, so the locations of Hidden Blocks are no longer shown. Version 3.0.0 introduces Red POW Boxes, wearable Red POW Blocks that activate upon hitting blocks three times before vanishing, and just like the actual block, it is exclusive to the Super Mario 3D World style.

Minecraft
In the Super Mario Mash-up in Minecraft, TNT is replaced by Red POW Blocks.