PIRLS has monitored trends in reading achievement at the fourth grade since 2001. PIRLS is administered every five years, making 2021 the fifth assessment of PIRLS.

PIRLS 2021 began the transition to digitalPIRLS, where countries can administer PIRLS 2021 in digital or paper format. digitalPIRLS includes ePIRLS.

ePIRLS monitors how well fourth grade students read online information.