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 damage enemies or drop any coins, but they instead 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, in which they are the only POW Block variant that makes an appearance. They cannot picked up, so they must be activated by hitting them normally. In addition, they start a chain reaction with one another when activated; while they cannot defeat on-screen enemies out of its range or drop midair coins, their tremors can hit nearby blocks.

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 exactly as they did in New Super Mario Bros. 2, releasing short-ranged shockwaves that hit and destroy blocks and enemies once hit. 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 it 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.