What happens when a row is completely filled in Tetris?

When a row is completely filled in Tetris, the row is cleared.

A completed horizontal line disappears from the playfield, and any blocks above it fall downward to fill the empty space. Clearing lines is the central objective of Tetris: players arrange falling pieces to create complete rows before the stack reaches the top of the board.

The game awards points for cleared lines, with the scoring usually increasing when multiple lines vanish at once. Clearing four lines simultaneously is called a “Tetris,” a term that gave the game its name. Different editions and game modes can use different scoring systems, bonuses, or visual effects, but line removal remains the defining mechanic.

A filled row does not normally make the piece itself disappear immediately when it lands; the row is checked and removed after the placement is completed. The game ends when the accumulated blocks prevent new pieces from entering the playfield, a condition often called topping out. This is why efficient line clearing matters: it creates space and keeps the stack from becoming too high.