HumanAttentionToken

HAT is a middleman-free ad network where advertisers pay verified humans directly for their attention using gasless USDC micropayments on Arc.

Viewers install a browser extension, verify their humanity with World ID, and earn USDC for every second they view ads — plus bonus HAT tokens as an incentive layer. Advertisers create campaigns, set their own per-second view rates and per-click bonuses, deposit USDC, and get real-time analytics on views, clicks, and spend.

The payment infrastructure uses Circle Gateway nanopayments on Arc — EIP-3009 signatures are signed offchain and batched into single on-chain transactions by Circle, making each micropayment effectively gas-free. Settlement runs automatically every 2 minutes via a Cloudflare Workers cron.

World ID 4.0 orb verification ensures every viewer is a unique, verified human — eliminating bot fraud entirely. No ad network takes a cut. No upfront budgets required. Advertisers pay exactly for what they get: $0.0001 per second of proven human attention.

The stack is a pnpm monorepo with 6 packages: a Cloudflare Workers backend (Hono + D1 SQLite), two React frontends (viewer site + advertiser console), a Chrome MV3 browser extension, shared TypeScript types, and Solidity contracts (Foundry).

The core payment flow runs on Arc Testnet where USDC is the native gas token (18 decimals natively, 6 decimals via ERC-20 — we handle both). When a viewer watches an ad, the extension tracks attention via IntersectionObserver with 15-second heartbeats. On session end, the backend calculates USDC earned at the advertiser's custom rate. Every 2 minutes, a Cloudflare Workers cron triggers settlement: it signs EIP-3009 TransferWithAuthorization messages offchain against Circle's GatewayWalletBatched contract (0x00777..., same deterministic address on every chain), then POSTs them to Circle's Gateway settle API. Circle batches all pending authorizations into a single on-chain transaction — zero gas per individual payment.

The hackiest part was reimplementing World ID v4's RP signing for Cloudflare Workers. The official @worldcoin/idkit-server package blocks non-Node.js environments, so we reverse-engineered the exact binary message format (version byte + 32-byte nonce + uint64 timestamps + keccak256-hashed action field-reduced to 32 bytes) and reimplemented EIP-191 signing with ethers.js — producing byte-identical signatures to the official library.

The extension opens the World ID verification page with ?autoclose=1, the QR widget auto-triggers, and after successful verification the tab auto-closes returning the user to where they were. The extension listens for chrome.storage changes to activate/deactivate the ad sidebar in real-time.

On top of USDC payments, the HAT token serves as an additional incentive layer exclusively for verified humans. It's an ERC-20 with a gas-optimized batchMint() that mints to all recipients in one transaction, proportional to USDC earned (10,000 HAT per $1 USDC by default). Since HAT is only minted to World ID-verified accounts, it functions as a proof-of-human-attention token — advertisers can optionally boost HAT rewards on their campaigns to attract more verified viewers, creating a secondary incentive market on top of the base USDC micropayments.

Advertisers set custom view rates and click bonuses per campaign, can pause/resume ads, withdraw unspent USDC, and see real-time analytics (views, unique viewers, CTR, spend breakdown by attention vs clicks).