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Add C2PA Label Easily with Capture API

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Add C2PA Label Easily with Capture API

This is the fourth installment of our Tech article series. The goal of this multipart series is to discuss provenance at a high level and provide more technically inclined readers a full dive into how to execute digital provenance. You can find the full list of this series here :

Part 1: What is Provenance and why we need it

Part 2: What is C2PA, Add C2PA easily with Capture

Part 3: Take True Photo with C2PA Watermark from Mobile Phones

Part 4 : You are here

Add C2PA easily with Capture API

In our last article, we explored adding C2PA watermarks from mobile phones using Capture Cam. While Capture Cam is great for individuals, what if you need to process assets in bulk?

Part of our solution for developers includes the Capture API. Using the Capture API, you can register all your assets in bulk, automatically if you wish! This powerful tool is part of the C2PA SDK provided by Numbers Protocol, ensuring seamless integration of provenance technology into your applications.


In order to register assets with Numbers Protocol, you will need to own a Capture account and acquire your Capture Authorization Token. You can refer to these materials if you do not have a Capture account or do not know how to acquire your authorization token.

Alternatively we have a video tutorial on how to acquire your Capture Token.

Register Digital Media File with Numbers Protocol

To register a media file with Numbers Protocol, we will be utilizing the Capture API, specifically the Registration API action. Using your preferred API platform or sending a curl request we can send the following POST request:


For this API call we will need to populate our Header with the Capture Authorization Token.

Authorization (string) token <Capture Token>
Content-Type (string) multipart/form-data

For the Register API action, the only required Body field is ‘asset_file’. If you wish to provide additional information such as metadata or captions you are free to do so. The following is the complete list of Body parameters you can send with the Register API action.

A successful API response will output a JSON with an ‘id’ field. See the example below:

This value is important and we will be needing it later.

Acquiring the C2PA Injected Generative AI Image

Having successfully registered the generative AI image to Numbers Blockchain, we can acquire the C2PA injected file by using the Capture API, specifically the Download asset with C2PA injection API action. Using your preferred API platform or sending a curl request we can send the following POST request:


Same like previously, for this C2PA API call we will need to populate our Header with our Authorization Token

Authorization Token <Capture Token>

Replacing the ‘{nid}’ parameter with the nid url parameter in the asset profile link from the previous step we get the following:

Navigating to the url we can see the C2PA injected image with an AI watermark, ensuring the authenticity of the generative AI content.:

The Role of IPTC

In addition to C2PA, the International Press Telecommunication Council (IPTC) sets important standards for metadata in news and media industries. IPTC's standards ensure that content is easily searchable, shareable, and verifiable across different platforms and systems. Integrating IPTC standards with C2PA enhances content authentication and verification processes, providing a comprehensive solution for maintaining content integrity and ownership.

As the need for provenance is growing in symmetry with the development of generative AI models. By applying C2PA standard, including AI watermarks, to all of your digital assets, you’ll be able to protect your contents and its ownership. This process is essential for content authentication and content verification. While currently there may be some limitations to C2PA, entities such as Numbers Protocol are actively working on improving the provenance solution!

Embrace Creativity with Capture

Capture empowers developers to secure and authenticate digital assets, creating a creative environment where content ownership is protected. By utilizing the Capture API and C2PA SDK, you can ensure that your creative works are properly registered, authenticated, and verified.

In our next article, we’ll explore how to verify your registered asset. Stay tuned!

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