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California AI Transparency Act in plain words.

Public AI tools in California that make or edit images, video, or audio must hide a label in what they make, where technically feasible. The label says if AI made or changed it. Large sites must read those labels from 2027.

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Status checked October 3, 2026. A plain guide, not legal advice.

Timeline of EU AI Act Article 50 and California AI Transparency Act dates from June 2026 to January 2028. A later California date, January 1, 2029, is not drawn.
The California AI Transparency ActCalifornia AI Transparency Act: California's law requiring generative AI providers to hide an AI disclosure in the images, video and audio they make or edit, and offer a free tool that reads it. and EU AI ActEU AI Act: The European Union's law on artificial intelligence, which includes rules for marking AI-made content. Article 50Article 50: The EU AI Act rule that AI-made content be marked in a form software can read, and deepfakes disclosed. run on one clock. Duties started in August 2026 and widen through 2029.

Key dates

  1. Law

    August 2, 2026: The Act (SB 942, delayed by AB 853) applies to AI providers.

  2. Law

    September 30, 2026: SB 1000 and AB 2713 are signed. SB 1000 takes effect that day.

  3. Law

    January 1, 2027: Large platforms and AI hosting sites take on their duties.

  4. Law

    January 1, 2028: New cameras and phones sold in California must offer the label.

  5. Law

    January 1, 2029: AI tools made to help people with disabilities are covered too.

Who it applies to

AI providers
A covered providerCovered provider: Under California law, anyone who makes a generative AI system that the public in California can use. is anyone whose AI tool is open to the public in California. There is no user floor now. Games with no user content are outside it. They must hide a latent disclosureLatent disclosure: Under California law, a hidden label inside a file that says which AI system made or changed it and when. in the images, video, and audio their AI makes or edits. They must also offer a free tool to check it.
Large online platforms
Social, file-sharing, group-chat, and search sites with over 2,000,000 users a month. From January 1, 2027 they must read provenance dataProvenance data: Under California law, information about where content came from and how it was changed, in a standards-based format., show it, and not knowingly strip it.
AI hosting sites
From January 1, 2027, they may not knowingly offer an AI model that skips the hidden label.
Camera and phone makers
New devices sold in California from January 1, 2028 must offer a hidden label for photos and recordings. It names the maker, device, and time. It is on by default.

A checklist for your team

Work through it with counsel. Each step names who usually owns it.

  1. Find your role.
    AI provider, large site, host, or device maker. Many firms are more than one.
    Legal
  2. Put the fields in every AI image, video, and audio file.
    Provider, tool and version, time, a unique ID, and whether AI made or changed it.
    Engineering
  3. Make the label hard to remove.
    Test crops, re-saves, and uploads. Pair the signed label with a watermarkWatermark: A mark placed in the content itself, visible or hidden, so it can be found again after the file is copied. where needed.
    Engineering
  4. Offer a free checking tool.
    It must take uploads and links and offer an APIAPI: Application programming interface: a way for one program to ask another to do a job, such as sign a file.. It may show personal data only with consent.
    Product
  5. Update licenses.
    Tell licensees their duties. Act within 72 hours when one breaks them.
    Legal
  6. Platforms: plan for January 1, 2027.
    Find labels, show what they say, and keep them on upload and download.
    Product

What changed on September 30, 2026

The Governor signed SB 1000 and AB 2713. SB 1000 is an urgency law, so it took effect that day.

California AI Transparency Act before and after SB 1000 and AB 2713
BeforeNow
Who must labelAI tools with over 1,000,000 usersCovered public AI tools, with no user threshold
What gets labeledWhat the AI madeWhat it makes or edits, but not minor edits
Media exemptionGames, TV, streams, and filmsOnly games with no user content
Free toolAn AI detectionAI detector: A model that guesses whether content was made by AI and returns a probability, not proof. toolA disclosure verification tool
Visible labelMust offer a manifest disclosureManifest disclosure: Under California law before SB 1000, a label people could see that says content was made by AI.No longer required
Hidden labelProvider, tool, time, and an IDThe same, plus whether AI made or changed it
Licensee breaks the rulesRevoke the licenseEnd it or notify within 72 hours
Platforms from 2027Show if data and a digital signatureDigital signature: Math that shows which key signed something and that it has not changed since. Any edit to the signed bytes breaks it. are "available"Show data "embedded" in, "attached" to, or "associated" with the file. Keep it on download. Skip data that fits no standard.

Where C2PA fits

Hard binding is a fingerprint of the exact file, so a re-encode breaks it. Soft binding is a watermark in the picture that still leads back to the label after a re-encode.
The fingerprint proves the file is unchanged. The watermark finds the label again when the file has changed or lost it.

A C2PA manifestC2PA manifest: The signed label itself: a small package inside a file that records who signed it, what they declared and how to check it. is a signed label. It can hold each field the hidden label needs, in the format big sites read. It shows who signed, what they said about AI, and if the file changed. The law also wants it hard to remove, and a tool to check it.

Encypher Mark adds a signed C2PA label to AI output, such as images, video, and audio. Anyone can check the result free. Open the checker.

What it means for publishers

A file signed with a label and a watermark loses its label when a site strips metadata; a checker finds the watermark, which points back to the signed record, shown as recovered.
If a site strips the label, a supported watermark can lead back to the signed record. The result says it was recovered.

The provider duties do not touch news text. But from 2027, large sites may not knowingly strip a standard signature. That includes a publisher's C2PA label. The law reaches large sites, not every feed or partner. So test your own path.

Good questions.

Does the law cover AI text?
Not the provider duties. They cover AI images, video, and audio. Text is outside them, even after SB 1000.
Does the law require C2PA?
No. It asks for data that follows a widely used standard. C2PA is the main open one, but the law names none.
Is a C2PA label alone enough?
Often not. The label holds the fields, but it must also be hard to remove. Many teams add a watermark. Test it, and let counsel decide.
What are the penalties?
$5,000 per violation. Each day counts as a new one. The detail on who can sue is in the engineer notes below.

Sources

  1. SB 942 (2024), the original Act Law
  2. AB 853 (Chapter 674, Statutes of 2025) Law
  3. SB 1000 (Chapter 861, Statutes of 2026) Law, in effect September 30, 2026
  4. SB 1000 status
  5. AB 2713 (Chapter 856, Statutes of 2026) Law, platform duties from January 1, 2027
  6. AB 2713 status

For engineers

Show the technical detail

The latent disclosure, field by field

Business and Professions Code 22757.3 as amended by SB 1000. One way to carry each field in a C2PAC2PA: The Coalition for Content Provenance and Authenticity: the group that publishes the open standard for content labels. manifest:

  • Provider name: the signer certificate and claim generator.
  • System name and version: claim_generator_info.
  • Time and date: the signed timestamp.
  • Unique identifier: the manifest instance ID.
  • Created or altered: a c2pa.created or c2pa.edited action with the digital source typeDigital source type: A field in the label that says how content was made: captured by a camera, made by AI, or a mix..
  • From 2029, assistive-technology status: a custom assertion.

Durability: the law wants a disclosure that is permanent or extraordinarily difficult to remove. A manifest can be stripped, so add a soft bindingSoft binding: A watermark or fingerprint that can find a content label again after the file was copied or its metadata stripped. that points back to it. Minor edits (brightness, crop, resize, format change, noise removal) do not count as alteration.

Enforcement

The Attorney General, a city attorney, or a county counsel can sue. Falsely claiming the assistive-technology delay costs $50,000 per violation until January 1, 2029.

The checking tool must output system provenance data and withhold personal data unless the person consents. A provider may point users to a third-party tool that meets the same rules; counsel decides whether a tool qualifies.

Keep reading

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