Integration Guide

Verify unique humans with Proof of Humanity V2 through CrossChainProofOfHumanity on Ethereum Mainnet and Gnosis Chain.

Proof of Humanity 2.0 Integration Guide

This guide is for developers who want to verify whether an address belongs to a registered human.

Integrators consume identity through CrossChainProofOfHumanity. PoH operators manage the registry through ProofOfHumanity. If you are integrating PoH into an application, you only need CrossChainProofOfHumanity.

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Quick start: Verify a human

Use CrossChainProofOfHumanity as the integration contract on every supported chain. It exposes both locally registered and synchronized cross-chain humanities.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

interface ICrossChainProofOfHumanity {
    function isHuman(address account) external view returns (bool);
    function humanityOf(address account) external view returns (bytes20);
}

contract HumanOnly {
    ICrossChainProofOfHumanity public immutable proofOfHumanity;

    error NotHuman();

    constructor(address crossChainProofOfHumanity) {
        proofOfHumanity = ICrossChainProofOfHumanity(crossChainProofOfHumanity);
    }

    modifier onlyHuman() {
        if (!proofOfHumanity.isHuman(msg.sender)) revert NotHuman();
        _;
    }

    function humanOnlyAction() external onlyHuman {
        // Application logic
    }
}

CrossChainProofOfHumanity addresses

Network	CrossChainProofOfHumanity
Ethereum Mainnet	0xa478095886659168E8812154fB0DE39F103E74b2
Gnosis Chain	0x16044E1063C08670f8653055A786b7CC2034d2b0

• Use isHuman(address) when you only need human verification.
• Use humanityOf(address) and store application data by humanity ID when identity must survive wallet changes.

Cross-chain state is delivered through bridge synchronization, so a recent registration, revocation, or transfer may not appear on another chain immediately.

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Identity lookup

Once you have a humanityId from humanityOf(address), these read-only functions provide additional detail:

function isClaimed(bytes20 _humanityId) external view returns (bool);
function boundTo(bytes20 _humanityId) external view returns (address);

Function	Purpose
isClaimed(humanityId)	Returns true if the humanity ID is actively claimed
boundTo(humanityId)	Returns the wallet address currently bound to a humanity ID

For the full status of a humanity (vouching state, pending requests, expiration, owner) via getHumanityInfo(humanityId), and for the registry management functions used by operators, see the Smart Contracts reference.

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Soulbound Identity Design

PoH V2 follows the principle: 1 human → 1 humanity ID ↔ 1 wallet address.

The humanityId is a soulbound identifier that persists across wallet transitions. If a user loses wallet access, they can re-register with a new address while keeping the same humanityId. Applications that key reputation, assets, or history by humanityId rather than by address preserve them across the user’s wallet changes.

humanity.owner == lostAddress      // Lost access
humanity.owner == address(0)       // Removal requested
humanity.owner == newAddress       // Re-registered with new wallet

V1 users have a humanityId equal to their original registration address (bytes20(address)). V2 users receive a new unique humanityId at registration. The isHuman() call automatically covers V1 registrations through the Fork Module.

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Registry contract addresses

Operators who manage the registry directly interact with ProofOfHumanity (and, on Ethereum Mainnet, ProofOfHumanityExtended).

Gnosis Chain

Contract	Address
ProofOfHumanity	0xa4AC94C4fa65Bb352eFa30e3408e64F72aC857bc
CrossChainProofOfHumanity	0x16044E1063C08670f8653055A786b7CC2034d2b0
AMB Bridge Gateway	0x6Ef5073d79c42531352d1bF5F584a7CBd270c6B1

Ethereum Mainnet

Contract	Address
ProofOfHumanityExtended	0xbE9834097A4E97689d9B667441acafb456D0480A
CrossChainProofOfHumanity	0xa478095886659168E8812154fB0DE39F103E74b2
AMB Bridge Gateway	0xddafACf8B4a5087Fc89950FF7155c76145376c1e
Fork Module	0x068a27Db9c3B8595D03be263d52c813cb2C99cCB

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What’s Next?

PoH Overview

Architecture and technical details

Smart Contracts

Core interfaces and data structures