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What is X402?
X402 is an HTTP402 Payment Required protocol for agents and applications. It lets clients pay for APIs and digital services directly over HTTP using:
- Off-chain, EIP-712 signed payment authorizations (EIP-3009 style)
- On-chain settlement executed by a facilitator service
Why X402 for Agentic Payments?
X402 is designed for human and AI clients that need to pay programmatically:Gasless UX
Users or agents sign authorizations; facilitators pay gas on-chain
Atomic
A single flow from authorization to settlement and distribution
Transparent
Clear audit trail of who authorized, who executed, and who received funds
HTTP-native
Uses standard HTTP status codes and headers, easy to integrate into existing APIs
Key Use Cases
- Metered API access paid per request
- Paywalled data and content unlocked on demand
- AI agents that autonomously pay for external tools and services
- Marketplaces and platforms that share revenue across multiple recipients
How X402 Works
At a high level, an X402 payment on Prism follows this Challenge → Authorize → Settle → Distribute flow:1
Challenge
Buyer calls a resource; the seller responds with
402 Payment Required and structured payment requirements (amount, asset, network, expiry, nonce scope)2
Authorize
Buyer (or its agent) signs an EIP-3009 authorization over the X402 token using EIP-712 typed data
3
Settle
The signed authorization is submitted to the X402 Facilitator, which validates and executes the on-chain transfer using
transferWithAuthorization4
Distribute
After settlement, the facilitator triggers Spectrum Registry to perform on-chain revenue splitting
Behind this flow, the facilitator offloads blockchain complexity (gas management, nonce tracking, retries) so sellers and agents can integrate using familiar HTTP patterns.