Base Verify Onchain

Base Verify Onchain

Base Verify Onchain lets your smart contract enforce one action per real person (airdrops, allowlists, votes, rewards) instead of one action per wallet, which anyone can create by the thousands.

A user proves they own a real account (like X, Coinbase, TikTok, or Instagram) through a normal sign-in, and optionally meets conditions you set (for example an active Coinbase One membership, or 1,000+ followers). Base signs a short-lived verification proving the user qualifies. Your contract checks that verification and records a one-way identity hash, so the same person can't act twice, even from a different wallet.

You never learn who the user is: no account, name, or personal data is shared with you, and the identity hash is irreversible. You also run no backend of your own. Your contract declares who is eligible, and Base does the checking and signing.

Available on Base Sepolia (testnet) during the test phase.

What you get

  • Sybil resistance onchain — dedupe on a one-way identity hash, enforced by your own contract.
  • No backend to run — your contract declares its policy; Base signs a verification your contract checks.
  • Privacy preserving — the verification reveals no provider, account, or conditions, only an irreversible hash.

Your users verify first

Base Verify Onchain assumes your users already hold a Base Verify credential for the provider your contract requires. Before claiming, a user verifies the relevant account — X, Coinbase, TikTok, or Instagram — once at verify.base.dev. Base stores that credential; your contract and app never see it.

If a user requests a verification without a credential for your provider, the API returns 404 verification_not_found — the signal to send them to verify first.

How integration works

  1. Deploy a contract that declares its eligibility policy and checks Base Verify verifications.
  2. In your app, have the user sign a message and exchange it for a verification from the Base Verify API.
  3. Submit the verification to your contract, which checks it and dedupes.

Next: Core concepts, then Integration.