California AI Transparency Act (SB 942, amended by AB 853)
AB 853 was signed October 13, 2025. Covered providers owe disclosures and detection tools from August 2, 2026. Large online platforms and generative AI hosting platforms are covered from January 1, 2027, including a ban on knowingly stripping provenance data. Capture device makers follow on January 1, 2028.
What it is
California's AI Transparency Act, originally SB 942, requires covered providers of generative systems with more than a million monthly users to offer a free detection tool and to include disclosures in output. AB 853, signed October 13, 2025, moved the provider date to August 2, 2026 and added two new classes: large online platforms, which from January 1, 2027 must detect and surface provenance data and must not knowingly strip it, and generative AI hosting platforms, which from the same date may not knowingly offer a system lacking the required disclosures. Capture device makers follow on January 1, 2028. It is the first US law that treats stripping provenance as a platform offence.
When to use this entry
Cite it for the US platform duty not to strip provenance and for the 2027 date.
Questions
When does California's AI Transparency Act take effect?
Provider duties from August 2, 2026; large platforms and hosting platforms from January 1, 2027; capture devices from January 1, 2028.
Does the California law apply to individuals who paraphrase text?
No. The duties fall on providers, large platforms, hosting platforms and device makers.