Networks & Token
x402 on HPP runs on two networks. Both are recognized natively by the @x402 SDK using their
CAIP-2 identifiers (eip155:<chainId>), and both settle in
the same USDC.e stablecoin.
Networks
- HPP Mainnet
- HPP Sepolia
| Field | Value |
|---|---|
| Network name | HPP Mainnet |
CAIP-2 (x402 network) | eip155:190415 |
| Chain ID | 190415 |
| RPC endpoint | https://mainnet.hpp.io |
| Block explorer | https://explorer.hpp.io/ |
| Gas token | ETH |
| Facilitator | https://facilitator.hpp.io |
| Field | Value |
|---|---|
| Network name | HPP Sepolia (testnet) |
CAIP-2 (x402 network) | eip155:181228 |
| Chain ID | 181228 |
| RPC endpoint | https://sepolia.hpp.io |
| Block explorer | https://sepolia-explorer.hpp.io/ |
| Gas token | ETH |
| Facilitator | https://facilitator-sepolia.hpp.io |
Get testnet ETH from the HPP Sepolia Faucet.
See Network Information for WSS endpoints and Chainlist links.
Token: USDC.e
All x402 payments on HPP settle in USDC.e (Bridged USDC). The contract address is the same on both networks:
| Field | Value |
|---|---|
| Symbol | USDC.e |
| Address (Mainnet & Sepolia) | 0x401eCb1D350407f13ba348573E5630B83638E30D |
| Decimals | 6 |
| EIP-712 domain name | Bridged USDC |
| EIP-712 domain version | 2 |
Because USDC.e has 6 decimals, prices in the x402 accepts are expressed as integer base units:
| Human price | amount (base units) |
|---|---|
$0.01 | 10000 |
$0.10 | 100000 |
$1.00 | 1000000 |
The EIP-712 domain (
Bridged USDC/ version2) matters forexact(EIP-3009) signatures. Register USDC.e as HPP's default asset in the SDK so it is filled in automatically — see the Quickstart: Sellers snippet.
Funding
Because every payment is denominated in USDC.e, a buyer needs a USDC.e balance before it can pay. The facilitator submits the settlement transaction and pays the gas, so a buyer normally needs no ETH.
- USDC.e. USDC.e is Bridged USDC. Bring it onto HPP by bridging from the parent chain — see the Bridge guide. For testnet USDC.e to run the quickstarts, reach out through Official Links.
- ETH (rarely needed). Only a buyer paying
uptoagainst a seller without EIP-2612 sponsoring needs a little ETH, for the one-time Permit2 approval. Get testnet ETH from the HPP Sepolia Faucet. Sellers/operators also need ETH to deploy contracts.
Verify a balance any time on the block explorer (mainnet) or Sepolia explorer by looking up the USDC.e contract above.