Google Releases Credentio, an Open-Source Tool for Verifying Media Authenticity Offline

Google has unveiled Credentio, an open-source C++ library that allows developers to verify the authenticity and provenance of media files—images, videos, audio, and documents—using the Coalition for Content Provenance and Authenticity (C2PA) standard. The library performs all validation work locally on a user's device, eliminating the need to send sensitive files to remote servers.

The timing reflects growing regulatory pressure: as governments worldwide implement AI transparency rules and content provenance standards, media applications must now demonstrate where their digital assets come from and whether they have been modified. Google built Credentio from the same internal technology that powers nearly 40 of its own C2PA-compliant products and has been tested at scale with tens of billions of generated assets across multiple file formats.

How It Works#

Credentio operates entirely offline within an application, letting developers pass media files and trust lists directly through an API. The library then examines the embedded C2PA metadata—manifests, assertions, digital signatures, and claim chains—to validate authenticity against known trusted authorities. Supporting both custom trust lists and the official C2PA Trust List, Credentio delivers a clear verdict report indicating which parts of the credential chain passed verification and where any integrity issues occurred.

Why Local Validation Matters#

By keeping validation local, Credentio addresses three pain points developers face with cloud-based alternatives:

• Privacy: Media files stay on the user's device and never reach Google or third-party servers.
• Speed: Results arrive instantly, even in high-volume workflows, without waiting for external API responses.
• Efficiency: No bandwidth is consumed sending large files to the cloud, and small memory overhead makes the library suitable for resource-constrained environments like mobile apps, desktop software, or edge servers.

This approach becomes particularly valuable when validating large assets—multi-gigabyte video files or high-resolution images—where uploading to a remote endpoint would be impractical.

What's Next#

The library currently focuses on validation. Google has announced plans to expand Credentio to include full credential generation and embedding capabilities, allowing developers to not only verify content but create and attach C2PA credentials directly to media files.