How Far Can Crimson Spread

Corrupt and Crimson variants can grow 6 tiles in all directions, and spread their biome up to three blocks away like any other source, but their spread can be contained with physical neutral barriers, like Clay or Wood.

How far of a gap can crimson spread?

Corruption, Crimson, and Hallow can jump up to three blocks to affect other blocks, and Corruption and Crimson can spread farther by using vines. You can prevent them from doing so by digging a 4 block wide channel.

How far down does crimson go?

Crimson and Hallow will spread through your world like wildfire, underground and all through your map, including snow biomes.