The game selects levels at random for the players to compete on.
If you are using a version of the game that includes this expansion, here are some key technical points from the PCGamingWiki : Super.Meat.Boy.Race.Mode.Edition.rar
Periodic rotations of hand-picked chapters created by the community, often featuring extreme difficulty. Technical Details and Requirements The game selects levels at random for the
Players can manually choose the chapters they want to race in, including the more difficult "Dark World" variants. Super Meat Boy is renowned for its "hard
Super Meat Boy is renowned for its "hard as nails" difficulty. While the Race Mode adds a competitive layer, the core gameplay remains focused on pixel-perfect wall-jumping and timing. Completing the most difficult sections, such as without dying, remains one of the hardest achievements in the game. Super Meat Boy Race Mode on Steam
A high-difficulty variant that pulls random levels from the massive "Super Meat World" community database.