Proof of Personhood

Proof of personhood addresses a problem pseudonymous blockchains cannot solve alone: confirming that a wallet is controlled by one distinct human rather than a bot or someone who spun up hundreds of throwaway addresses. Instead of checking legal identity, most schemes issue a portable, often privacy-preserving credential proving a wallet passed a uniqueness check, letting an app trust "one person, one account" as a lightweight complement to digital identity systems, without learning who the person actually is.

The highest-assurance method is hardware biometrics. World ID, built by Tools for Humanity (Sam Altman's Worldcoin project), scans a user's iris with a spherical "Orb" device and converts it into a unique code that flags duplicate signups without storing the raw image. Lower-friction, non-biometric alternatives exist too: BrightID builds a vouched social graph of connections, while Gitcoin Passport aggregates smaller trust signals, such as verified social accounts and wallet age, into a composite score.

Applications include fair token airdrops that filter out Sybil attack farms, one-person-one-vote governance, quadratic funding rounds, and proposed universal basic income pilots. In 2026, World has also pushed proof of personhood toward verifying humans interacting with AI agents, as automated bots increasingly mimic real users online.

The tradeoffs mirror the approach: biometric collection raises centralization and surveillance concerns and has faced regulatory pushback in several countries, while social-graph methods stay vulnerable to collusion rings and paid identity farming.