Proof-of-personhood is a security and privacy concept for showing that a real human, not a bot or automated agent, is behind an online action. The goal is to confirm “a person is present” without necessarily exposing civil identity, biometrics, or other unnecessary personal data.
It matters because many abuses on the web depend on automation: spam, account creation, scraping, vote manipulation, and abuse of rate limits. Traditional CAPTCHAs and anti-bot filters can slow these attacks, but they are often weak on their own and can harm accessibility. Proof-of-personhood aims to add a stronger signal that a session is backed by a unique human while preserving privacy.
In practice, this idea appears in layered defenses: challenge-response checks, device-bound credentials, reputation signals, and selective disclosure systems that reveal only what a service needs to know. The main security tradeoff is balance: too little assurance lets bots through; too much can create tracking, exclusion, or centralized identity control.