New state requirements take effect for large gatherings called "mega events."
Starting Tuesday, any indoor event in California with 1,000 or more attendees must require proof of a COVID vaccination or negative test result. Visitors are not allowed to self-attest they have had a vaccination.
These rules apply to venues like theme parks, sport arenas, and convention halls.
Outdoor gatherings with 10,000 or more people are also categorized as mega events, but the California Department of Public Health is only recommending that venues check the vaccination status of attendees. Unlike the rules for indoor events, providing proof is not required.
Parts of the Bay Area have rules that are stricter than the state's bar. San Francisco, Berkeley and Contra Costa County all require proof of vaccination for entering restaurants, gyms and other indoor settings.
The change in the state rules for so-called mega events comes as California has shown recent success against the COVID pandemic.
Data shows that California has the lowest coronavirus case rate in the United States.
The state was the only one in the country to make it into the Centers for Diseases and Prevention's category of substantial community spread of the coronavirus. The rest of the country is in the high transmission category.