The largest number of housing units subject to rent control can be found in California, but the policy environment is quite complex and is characterized by a series of interacting state and local laws. This complexity represents a significant barrier for researchers and policymakers seeking a clear and accurate picture of how rent control works in California, and how it incentivizes different behaviors among landlords and tenants alike. This technical report surveys rent control rules in California, with special attention paid to the recent statewide rent caps, historic developments, and the systems in Los Angeles and San Francisco. This report should be regarded as a selective snapshot of the current system, and researchers interested in pursuing their own analyses involving the California systems are encouraged to conduct supplemental legal research. This paper will be updated on a rolling basis as further information comes to light.