https://www.siliconvalley.com/2021/07/30/vaccine-card-which-bay-area-music-clubs-movie-theaters-other-venues-are-requiring-it/

As the COVID-19 delta variant surges, an increasing number of Bay Area entertainment venues are requiring proof of vaccination from their customers.

Many establishments will accept digital copies of your vaccine record; that information is available for your phone from https://myvaccinerecord.cdph.ca.gov.