What is proof of personhood?

A way to show that an online account belongs to one real, unique human without revealing their identity. It defends against Sybil attacks, where one actor runs many fake accounts.

What is the difference between proof of personhood and KYC?

KYC proves who you are, usually with documents and a selfie. Proof of personhood only proves that you are a distinct living person.

Is there a proof of personhood without biometrics?

Yes. Approaches include social vouching, document-based credentials and in-person events (pseudonym parties). Hour of Humans uses short in-person check-ins with strangers and stores no biometric data.

Is World (Worldcoin) the only option?

No. It is the best-known biometric approach, using an iris scan. Others rely on documents, social graphs or meeting in person.

Proof of human, proof of humanity, personhood credentials

Proof of personhood, without an iris scan

Proof of personhood means showing that an account belongs to one real, unique human, without showing which human. It is the missing piece of the online world now that AI can write, talk and fill in forms like a person.

Why it matters now

CAPTCHAs were built to stop simple scripts. Modern AI solves most of them, and click farms solve the rest for a fraction of a cent. Meanwhile, anything that counts people online (polls, votes, sign-up bonuses, reviews, free tiers) can be flooded with fake accounts. This is called a Sybil attack: one actor pretending to be many.

Classic identity checks (KYC: a passport photo plus a selfie) prove who you are, which is more than most sites need and creates a pile of sensitive data. Proof of personhood asks a smaller question: are you a person, and only one?

The main approaches

Biometrics. Scan something unique about your body, such as the iris, and keep a code that proves uniqueness. Strong against duplicates, but it needs special hardware and asks people to trust whoever holds the biometric system. World (formerly Worldcoin) is the best-known example.
Documents. Government ID or a bank account, sometimes wrapped in cryptography so only "is a unique person" is shared. Works where people have documents and are willing to show them.
Social vouching. People who know you vouch for you; a web of trust. Cheap, but it can be gamed by groups who vouch for fake members.
Pseudonym parties. Everyone shows up in person, at the same time, in many places. Since a body can only be in one place at once, each attendee gets exactly one token, with no name attached. The idea was described by researchers Bryan Ford and Jacob Strauss in 2008.

An offline, anonymous version

Hour of Humans is a small working version of the pseudonym-party idea. You tap and get a random number, stored only on your phone. When 300 people in your city have tapped, the city gets its Hour: a Saturday afternoon, a busy public place, 30 minutes. The page groups you with two or three strangers; you show each other short codes, put all phones in one pile and count that there are as many phones as people. Two confirmations and your number turns green.

Numbers that never show up are deleted at the end of each season, and everyone shows up again next season, so a body cannot be sold twice. We keep a random number, the city and whether you came. No name, email, photo, document, exact location or IP address.

Trade-offs, honestly

It only works where enough people take part; a city with no Hour proves nothing yet.
It is weaker than biometrics against a determined group that brings extra phones; the phone pile and the count are there to make that expensive, not impossible.
It costs people half an hour, a few times a year. In return nobody has to scan anything or trust us with who they are.