How does the many-worlds interpretation of quantum mechanics relate to a multiverse?

The many-worlds interpretation (MWI) of quantum mechanics relates to the concept of a multiverse by proposing that every possible outcome of a quantum measurement actually occurs, but in separate, noninteracting branches of reality.12

In standard quantum theory, a system exists in a superposition of states until a measurement is performed, at which point the wave function appears to collapse into a single, definite outcome. Physicist Hugh Everett proposed that this "collapse" is an illusion caused by treating the measuring apparatus classically. Instead, MWI suggests that the observer and the apparatus become part of the quantum system, causing the universe to branch into multiple, mathematically unified worlds. In this framework, every potential history or experimental result is realized in its own distinct universe.21

While this model provides a way to avoid the paradoxes associated with wave-function collapse, it is considered a type of multiverse because it asserts the existence of a vast number of parallel worlds. Unlike inflationary multiverse models, which involve regions of space-time, the MWI multiverse is defined by the branching of quantum states.1