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C2PA implementation guide

Send content to our APIAPI: Application programming interface: a way for one program to ask another to do a job, such as sign a file. in one call and get it back with a C2PA labelC2PA manifest: The signed label itself: a small package inside a file that records who signed it, what they declared and how to check it.. Anyone can then check it for free, with no account.

Get your API keyAPI reference
Send a file to the signing API, get it back signed with the label inside, and anyone can check it for free without an Encypher account.
Send the file to the API. Get it back signed. Anyone checks it, free.
Sign
One call for text, one for files.
Check
A public call. No key needed.
Docs
Every field and error in the API reference.
Formats
75+ formats for signing and verification.

Three steps to a signed file

  1. Get a key.

    Make a free account and copy your API keyAPI key: A secret string that identifies your account when your software calls an API. Keep it out of public code..

    Create an account

  2. Send the content.

    Post text or a file. The API adds the label and signs it.

  3. Publish the signed copy.

    Serve what comes back. It looks the same to readers.

Where to sign in your stack

Signing takes four steps: your content, sign it with your key, the label goes inside, publish as usual.
Sign at one point: after the content is final and before it goes out.
WordPress
Sign on publish. Our plugin does it for you.
Other CMS
Listen for the publish event, sign, then save the signed copy.
Static sites
Sign at build time. No signing at run time.
AI apps
Sign after the model answers and before the user sees it.

How checking works

Four of the five answers a provenance check can give: Verified, Modified after signing, Issuer not recognized, and No provenance found. The fifth is Could not verify.
The public check gives one of four plain answers.

The check is a public call. It needs no key and no account. Any app that follows C2PAC2PA: The Coalition for Content Provenance and Authenticity: the group that publishes the open standard for content labels. can check files we sign, too.

The result shows who signed, what they declared, and if the content changed. It does not say the content is true. Try the free checker.

What it costs

Publishers sign free for normal publishing. Fair-use limits apply. Teams marking AI output get 1,000 outputs a month on the free trial.

Your own company name on the label comes with a paid plan. See pricing.

For engineers

Show the technical detail

Quickstart code

curl -X POST https://api.encypher.com/api/v1/sign \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: $(uuidgen)" \
  -d '{
    "text": "Your article text.",
    "document_title": "My article",
    "options": { "segmentation_level": "sentence" }
  }'

Signing options for text

segmentation_level
document (default), sentence, paragraph or section. Sentence gives per-sentence checks.
manifest_mode
full (default) or micro, a compact per-segment marker.
digital_source_type
An IPTC digital source type, such as trainedAlgorithmicMedia for AI output.
rights
Rights metadata: copyright holder, license URL, and AI training, inference and data mining permissions.
use_rights_profile
Embed your saved rights profile instead of passing rights each time.

Every field, response and error code is in the API reference. Send an Idempotency-Key on sign calls so a retry does not sign twice.

Keep reading

Create. Mark. Endure.

Get a free key and sign your first file today.

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