Provenance standard
C2PA (Coalition for Content Provenance and Authenticity) is an open technical standard for attaching a signed, tamper-evident history to a media file. It's the most durable answer to 'was this AI?' that currently exists — when it's actually present.
How it works
A C2PA-compliant file carries a "manifest": a structured, digitally signed record of assertions — who or what created the asset, what tools touched it, and in what order. Assertions are hashed and chained, so any later edit either extends the manifest (if made with a compliant tool) or breaks the signature (if the file is edited with a tool that strips or ignores it, which is most tools today). The manifest is typically embedded in the file itself, in JUMBF format inside JPEG/PNG/HEIC containers, or as XMP metadata pointing to it.
An IPTC-defined vocabulary term the manifest can carry, with values including trainedAlgorithmicMedia (fully AI-generated), compositeWithTrainedAlgorithmicMedia (AI-assisted composite) and digitalCapture (camera original). This is the single most direct machine-readable "this was AI" signal currently standardized.
The manifest is signed with a certificate chain back to an issuing authority (a camera maker, a generator vendor, a publisher). A valid signature means the recorded history hasn't been altered since signing — it does not mean the history is complete or that no earlier, unsigned edit happened before the chain started.
Adobe (Firefly, Photoshop), several camera makers, and some newsrooms support C2PA to varying degrees. Most social platforms strip it on upload today, and most images in general circulation carry no manifest at all — its absence tells you nothing about origin.
In practice
Treat C2PA the way you'd treat any signed document: a real credential when present is strong evidence, and its absence is simply "no credential," not "suspicious." Check for it, but build your workflow — reverse image search, metadata inspection, visual review — around the assumption that most files you check won't have one yet.
FAQ
A valid, present manifest is strong evidence for whatever it asserts. A missing manifest proves nothing — most images online were never issued one.
The signature chain resists tampering with an existing manifest, but a bad actor can simply use a tool that doesn't attach one, or strip it before distribution. It's a provenance record, not an unbreakable seal on every image.
Inconsistently. Many platforms recompress or resave uploads in ways that strip embedded manifests, though some are adding support to preserve or display credential badges.
Worked example
Simplified, a C2PA manifest for an AI-generated image carries a chain of assertions similar in spirit to: creator tool = "Adobe Firefly 3", action = "created", digitalSourceType = "trainedAlgorithmicMedia", timestamp, and a signing certificate identifying the issuer. Each assertion is hashed, the hashes are chained together, and the chain is signed. Software that respects C2PA (rather than stripping it) reads that chain and can display a "Content Credentials" badge; software that doesn't simply passes the file through, credential intact but unread, or discards it during recompression.
Comparing provenance signals
| Signal | Tamper resistance | Survives social re-upload? | Tells you |
|---|---|---|---|
| C2PA manifest | High — cryptographically signed chain | Rarely — most platforms still strip it | Structured, standardized origin claim (digitalSourceType) |
| EXIF (JPEG) | Low — plain fields, easily edited | Rarely — stripped on upload by most platforms | Camera Make/Model, software, timestamps |
| PNG text chunks | Low — plain text, easily edited or stripped | Rarely — most re-encoding drops ancillary chunks | Full generator prompt/parameters, when present |
Takeaway
All three are genuinely useful when you have the original, unshared file. All three are usually gone by the time an image has been through Instagram, WhatsApp or a screenshot. Build a verification workflow — reverse image search, visual review, source context — that doesn't depend on metadata surviving.