Citation: The LEGO Group - LEGO DUPLO (LEGO History) (Article), Accessed January 22, 2026.

For a large brick to become part of the LEGO System, it must be capable of interlocking with the standard LEGO brick. Many variations of a 2:1 brick are made, and eventually a solution is created by hollowing out the studs on the brick, making it possible to plug the tubes of a standard LEGO brick into the hollow studs. The new brick is called DUPLO deriving from the Latin word for “double” because of the brick’s 2:1 scale being twice the size of a standard LEGO brick on all dimensions.

The new construction method of combining large and small elements is patented in 1967. In 1968 LEGO DUPLO bricks are tested on the Swedish market, and after a few adjustments the brick is launched globally in 1969.

DUPLO debuted globally in 1969. The hollow stud on DUPLO bricks was required to make it compatible with LEGO bricks.