What is x402? The HTTP 402 Protocol for Native Web Payments

x402 is an open-source protocol that revives the HTTP 402 “Payment Required” status code to enable seamless, on-chain payments for web resources using stablecoins. It transforms traditional web interactions into programmable, blockchain-native transactions, allowing AI agents, users, and services to pay for APIs, data, or content without intermediaries.

Origins and Purpose

The HTTP 402 code was reserved in the original RFC 9110 for future payment mechanisms but remained unused. x402, developed by Coinbase in 2025, activates it for crypto-native payments, addressing the gap between Web2 infrastructure and Web3 economies. The protocol enables direct stablecoin transfers (USDC, USDT) for access to premium content, computations, or services, reducing friction in AI-driven commerce and micropayments.

How x402 Works

x402 integrates with existing web servers and clients:

• Payment Request: A server responds with 402 and a Payment Payload, specifying amount, asset, and chain.
• Client Action: The user or AI agent signs a transaction via wallet or agent.
• Verification & Settlement: A facilitator (optional) verifies signatures and settles on-chain, returning access upon confirmation.

Key endpoints include /verify for payload validation and /settle for execution. It supports EVM chains like Ethereum, Base, and Avalanche, with gasless options via EIP-7702 and Account Abstraction.

Key Features

• Native Web Integration: No plugins; works with standard HTTP.
• AI Agent Compatibility: Autonomous payments for data or APIs.
• Multi-Chain Support: Ethereum, Solana, Base; cross-chain bridges.
• Facilitator Layer: Shared infrastructure for verification, settlement, and discovery (/list endpoint).
• Security: Idempotency, replay protection, ZK proofs for privacy.

x402 abstracts blockchain complexity, offering consistent APIs for merchants and apps.

Benefits and Use Cases

x402 unlocks:

• Micropayments: Pay per API call or dataset access.
• AI Commerce: Agents transact for computations without human input.
• Content Monetization: Creators charge for premium articles or videos.
• Enterprise Tools: Confidential transfers for compliance.

In 2025’s $300 billion stablecoin market, x402 reduces costs by 90% for high-frequency interactions.

Ecosystem and Future

Backed by Coinbase, Cloudflare, Visa, and Google, x402 includes projects like PING (first token mint), Kite AI (agent identity), and PayAI (facilitators). Future enhancements: USDT Transfer Aggregator and Guaranteed Blockspace for institutions.

In summary, x402 revolutionizes web payments, blending HTTP with blockchain for a programmable, agentic economy.