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Verifiable
Credentials

Technical specifications, implementation patterns, and real-world use cases for W3C Verifiable Credentials. From issuance to revocation, learn how VCs work in production.

What Are Verifiable Credentials?

A Verifiable Credential (VC) is a tamper-evident, cryptographically verifiable digital credential. Unlike physical credentials or simple digital documents (PDFs), VCs include cryptographic proofs — signatures from the issuer that can be verified independently without contacting the issuer.

The W3C Verifiable Credentials Data Model (VCDM) is the canonical standard. A VC contains claims about a subject (e.g., "over 18", "license to drive", "employee ID"), alongside metadata about the issuer, validity period, and cryptographic proof.

VC Formats Compared

Format	Encoding	Selective Disclosure	Zero-Knowledge	Best For
JWT-VC	Base64-encoded JSON	No (full credential)	No	Simple issuance, enterprise
SD-JWT	Selective Disclosure JWT	Yes (per-claim hashes)	No	Selective disclosure without ZK
ISO mDoc	CBOR	Yes (per-element)	Partial	Mobile driving licenses
AnonCreds	JSON	Yes	Yes	Privacy-critical government

Implementation Pattern

{
  "@context": [
    "https://www.w3.org/ns/credentials/v2",
    "https://www.w3.org/ns/credentials/examples/v2"
  ],
  "id": "urn:uuid:3978344f-8596-4c3a-a978-8fcaba3903c5",
  "type": ["VerifiableCredential", "IdentityCredential"],
  "issuer": "did:polygon:0x1234...5678",
  "validFrom": "2025-01-01T00:00:00Z",
  "validUntil": "2028-01-01T00:00:00Z",
  "credentialSubject": {
    "id": "did:polygon:0xabcd...ef01",
    "givenName": "Jane",
    "familyName": "Citizen",
    "dateOfBirth": "1990-06-15",
    "nationality": "BT"
  },
  "credentialStatus": {
    "id": "https://registry.example.com/status/123",
    "type": "StatusList2021Entry"
  },
  "proof": {
    "type": "Ed25519Signature2020",
    "created": "2025-01-01T00:00:00Z",
    "verificationMethod": "did:polygon:0x1234...5678#key-1",
    "proofPurpose": "assertionMethod",
    "proofValue": "z3cxb5..."
  }
}

W3C VCDM v2 example — a foundational identity credential with selective disclosure support and revocation status.

Revocation Mechanisms

StatusList2021

The W3C standard for credential revocation uses a bitstring list. Each credential is assigned an index in a status list. The issuer updates the bit at that index to revoke. Verifiers check the list without learning which other credentials are revoked.

Accumulator-based

Zero-knowledge friendly revocation using cryptographic accumulators. Used with AnonCreds. Supports privacy-preserving revocation checks without revealing the credential's position in a list.

DID-based

The issuer's DID document can advertise revocation endpoints or deactivate the DID key used for issuance. Simple but lacks granularity — affects all credentials from that issuer key.