This brief from theLearning Policy Institute describes California’s commitment to making prekindergarten (PreK) universal through the expansion of transitional kindergarten (TK) and other state-funded programs. Between 2021–22 and 2023–24, TK enrollment doubled, from about 75,000 to over 151,000 children. Approximately 59% of eligible 4-year-olds enrolled in TK in 2023–24. Across publicly funded PreK programs—TK, the California State Preschool Program, and Head Start—California went from serving about 34% of all 4-year-olds to 50% between 2019–20 and 2023–24. Enrollment of 4-year-olds climbed from about 37% to 55% during that time when also considering subsidized child care. These data are promising both in absolute terms and relative to trends in other states, although more information is needed to understand whether programs are high quality and access is equitable. This brief is particularly useful for teacher and leader educator programs in California or states considering or undergoing similar expansions.