Integration

You build two things — a contract that declares your policy and checks verifications, and an app that fetches verifications — and point both at Base Verify.

What you'll need

Input	Value (Base Sepolia)
SignerRegistry	`0x4f15593fbF7e3491d15080e1610E7AF8deBA1a02`
API base URL	`https://verify.base.dev/v1`
Chain	Base Sepolia (`84532`)
Consumer base	`BaseVerifyConsumer.sol` (from Base Verify)

Deployed example contracts (Base Sepolia)

Two working consumers you can inspect on Basescan, both extending BaseVerifyConsumer and calling the registry above:

ExampleCBOneAirdrop (gates on an active Coinbase One membership)
ExampleAirdropXVerified (gates on a verified X account)

1. Write your contract

Extend the Base Verify consumer base so your policy is readable onchain, check verifications through the registry, and dedupe on identityHash.

import {BaseVerifyConsumer, Condition} from "@baseverify/BaseVerifyConsumer.sol";

contract MyAirdrop is BaseVerifyConsumer {
    mapping(bytes32 => bool) public claimed;
    error AlreadyClaimed();

    // Base Verify registry address for your chain.
    constructor(address registry_) BaseVerifyConsumer(registry_) {}

    // Your eligibility policy — must be constant.
    function provider() external pure override returns (string memory) {
        return "coinbase";
    }

    function conditions() external pure override returns (Condition[] memory) {
        Condition[] memory c = new Condition[](1);
        c[0] = Condition("coinbase_one_active", "eq", "true");
        return c;
    }

    function claim(bytes32 identityHash, uint40 expiration, bytes calldata signature) external {
        if (claimed[identityHash]) revert AlreadyClaimed();
        _verify(identityHash, expiration, signature); // binds msg.sender; reverts on a bad or expired verification
        claimed[identityHash] = true;
        // ... your reward logic ...
    }
}

provider() and conditions() must be immutable constants — a changing policy invalidates outstanding verifications and breaks dedupe.

Optionally override cutoffBlock() to require a credential no older than a given block; unlike provider/conditions it isn't part of policyHash, so you can change it without invalidating outstanding verifications. See Core concepts.

2. Fetch a verification in your app

Have the user sign a SIWE message that names your contract, then POST it to the Base Verify API. Pass the response to your contract's claim function.

import { createSiweMessage, generateSiweNonce } from "viem/siwe";

// The statement and Resources line below are required by the API.
const message = createSiweMessage({
  domain: window.location.host,
  address: userAddress,
  statement: "Claim eligibility for a Base Verify onchain benefit.",
  uri: window.location.origin,
  version: "1",
  chainId: 84532,
  nonce: generateSiweNonce(),
  resources: [`eip155:84532:${MY_CONTRACT_ADDRESS}`],
});

const signature = await signMessageAsync({ message });

const res = await fetch("https://verify.base.dev/v1/onchain_verifications", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({ message, signature }),
});
const { identityHash, expiration, signature } = await res.json();

await writeContract({
  address: MY_CONTRACT_ADDRESS,
  abi,
  functionName: "claim",
  args: [identityHash, expiration, signature],
});

See the API reference for the full request, response, and errors.