On-chain subscribe path · Arbitrum Sepolia

Set up the on-chain subscribe path

This page sets up the on-chain subscribe flow, which runs on Arbitrum Sepolia (an Ethereum L2 testnet, audit-gated). Everything below is free — testnet ETH for gas and a public mint for testnet USDC. About 10 minutes end-to-end. Pay-per-call x402 buys settle on Base mainnet and need none of this.

Two rails. x402 pay-per-call — including the flagship address-reputation verdict — settles in USDC on Base mainnet (eip155:8453), no testnet setup needed (quickstart). The on-chain subscribe flow and the EIP-712 attestation domain on this page run on Arbitrum Sepolia (chainId 421614) — audit-gated, mainnet anchor pending.

Step 1

Install a wallet

Any EVM wallet works. We recommend MetaMask or Rabby. The site will detect your wallet automatically once it's installed.

Step 2

Add Arbitrum Sepolia to your wallet

Click below to add the network. Your wallet will show a confirmation prompt — accept it, then switch to Arbitrum Sepolia in your wallet's network selector.

Add manually instead

Network name: Arbitrum Sepolia
RPC URL: https://sepolia-rollup.arbitrum.io/rpc
Chain ID: 421614
Currency: ETH
Block explorer: https://sepolia.arbiscan.io

Step 3

Get testnet ETH for gas

You need a tiny amount of testnet ETH to pay for transactions on Arbitrum Sepolia. The fastest path is a direct Arbitrum Sepolia faucet — pick whichever has the shortest queue:

Alchemy Arbitrum Sepolia faucet ↗

Direct Arbitrum Sepolia ETH. Requires Alchemy account (free).

QuickNode multi-chain faucet ↗

Direct Arbitrum Sepolia ETH. Requires QuickNode account (free).

Triangle Platform faucet ↗

No login. ~0.01 ETH per request.

Bware Labs faucet ↗

Free. Twitter login.

Or get Sepolia ETH (L1) and bridge to Arbitrum

If the direct faucets are dry, get Ethereum Sepolia ETH first, then bridge to Arbitrum Sepolia.

Sepolia POW Faucet ↗

Mine in-browser, no login. Slow but reliable.

Alchemy Sepolia Faucet ↗

Requires Alchemy account.

Google Cloud Web3 faucet ↗

Requires Google account.

Then bridge L1 → L2 via the official Arbitrum bridge ↗ (10–15 min for the deposit to land on L2).

Step 4

Get testnet USDC

Feeds are paid for per byte in USDC. On testnet we use a MockUSDC contract with a public mint function — self-serve any amount.

Connect a wallet first.

Step 5

Approve a USDC allowance

Approve the DataStream settlement contract to pull USDC from your wallet as data is delivered. One-time approval, with a spend cap you set. (The site can also prompt for this on your first subscribe — same result.)

Step 6

You're ready

Browse the feeds →

Find a feed, subscribe, and start consuming live data — settled per byte in USDC.

Verify

See ForeSeal →

Verify before your agent acts — watch the demo refuse four attacks, then drop in the Kit or Gate.

Reference

Contract addresses

DataRegistry: 0x086990937Cf931e36E01487CD63407f281f1Fc6A
DataStream: 0x44729bB148F46d8Db509E47b0453edc271e06e95
SchemaRegistry: 0x4102BA342A3e9f495bD553D99D1590470C32EE88
USDC: 0x1c16659aeb3aE28467E90348fAAB8874a0D3A4d3

Trouble?

Common problems

"Insufficient funds for gas" — your wallet's on the wrong network (mainnet?) or you have no testnet ETH yet. Re-check Step 2 and Step 3.
Subscribed but receiving no data — your USDC balance is below the per-call fee, or the DataStream allowance was revoked. The contract skips delivery silently. Re-check Steps 4 + 5.
Need help? How it works walks through the full flow.