World ID is built for easy integration, but here are a few core concepts that are helpful to understand before you start.

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Proof of Personhood

“Proof of Personhood” is distinct from many existing identity systems. It is a way to prove that a person is unique, without revealing any personal information. World ID is not KYC, and it does not disclose your identity or previous actions to anyone. World ID supports multiple “Verification Levels” to prove that a person is a unique human. These levels provide different degrees of humanness assurance, accessibility, and protection against fraud.
Verification LevelHumanness LevelDescription
Orb+Orb+
Very Strong[Coming soon] Orb verification, plus authentication which verifies the person using World ID is the legitimate holder.
OrbOrb
StrongBiometric verification, uniqueness through iris (details).
Secure DocumentSecure Document
HighDocument verification eg. Passport with security chip verification
DocumentDocument
HighDocument verification eg. Passport
DeviceDevice
MediumUnique mobile device check.

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Vocabulary

Some terms are used throughout the World ID documentation. Here are a few of the most important ones:
  • World ID: A user’s self-custodial identity, as well as the name of the protocol.
  • App ID: The ID of your app that is assigned in our Developer Portal.
  • Action: A developer-facing primitive that lets you put any app operation behind a unique-human gate. An app can have one or more actions depending on your use case.
  • Zero-Knowledge Proof (ZKP): A cryptographic method to prove that a statement is true without revealing any information about the statement itself. World ID uses ZKPs to prove that a user is verified without revealing the user’s identity.
  • Nullifier Hash: A component of the World ID ZKP; a unique identifier for a combination of a user, app_id, and action.
  • Signal: A component of the World ID ZKP; data attached to the proof that cannot be tampered with. An example may be a user’s choice for an election.
  • Merkle Root: A component of the World ID ZKP; The root of the Merkle Tree that identity commitments are inserted to.
It’s important to note the difference between the two types of verification, depending on the context:
  • Orb/Passport Verification: A user’s identity can be verified through either an Orb, Device or Passport and their identity commitment is then recorded on the blockchain.
  • Proof Verification: The process of validating a user’s Zero-Knowledge Proof (ZKP) either off-chain via a REST endpoint we host or on-chain using our Smart Contracts.