Coinbase unveiled an open-source protocol for on-chain payments via HTTP called x402.
Announced on May 6, the system repurposes the previously unused HTTP 402 “Payment Required” status code to support direct machine-native payments using stablecoins.
The protocol enables autonomous agents and applications to pay for API access, data, and services without relying on human intervention, subscriptions, or traditional payment infrastructures.
Business models and use cases
The core design of x402 enables a server to issue an HTTP 402 response with payment instructions when a client requests a paid resource. Upon receiving the payment requirement, the client, whether a human user or an autonomous agent, can initiate an on-chain transaction and retry the request with a signed payment.
This architecture enables microtransactions for content access, context retrieval, and AI inference, making per-use monetization technically feasible and economically viable. x402 is currently available as an open standard with a reference implementation on Coinbase’s GitHub and developer site.
According to the exchange, it will open the roadmap for community contributions and decentralized governance in upcoming iterations.
The x402 design supports frictionless micropayments across various sectors. In practical terms, AI agents can pay for API access per call, monetize content per article or stream, and sell cloud computing resources by the second or gigabyte.
The project’s white paper describes real-world use cases, including per-play gaming models, per-inference AI services, and per-article paywalls for publishers.
The protocol also aims to simplify compliance and operational burdens by eliminating the need for PCI certification and exposure to chargebacks. Once confirmed on-chain, all transactions are final, and payment processing is entirely decentralized.
Autonomous transactions
According to the project’s white paper, x402 addresses long-standing inefficiencies in existing payment systems that rely on account-based setups, delayed settlement, and centralized control.
Traditional payment methods such as ACH and credit cards introduce latency, chargeback risk, and human-driven onboarding steps, all incompatible with machine-to-machine (M2M) applications or autonomous AI workflows.
By contrast, x402 enables low-latency, irreversible payments with settlement times averaging 200 milliseconds when deployed on rollups.
The protocol executes payments using stablecoins, with a chain-agnostic design that allows support for multiple blockchains and tokens.
Additionally, x402 facilitates real-time revenue collection through client-server communication that directly integrates signed payments into HTTP requests, eliminating the need for API keys, pre-registration, or manual invoicing.
Developer integration
The x402 protocol supports a JSON payment request format embedded in the HTTP 402 response. To prevent replay attacks, the server specifies payment details, including the recipient wallet address, network identifier, asset contract address, payment expiration, and a nonce.
Clients respond by signing a payment authorization using the EIP-712 standard, which is broadcast on-chain to complete the transaction.
EIP-712 defines a framework for structuring, hashing, and signing typed data. It aims to make data signing on Ethereum more human-readable and verifiable.
Coinbase provides middleware libraries for Node.js and browser environments, allowing integration with one line of code. The x402 structure also uses wallet interfaces to confirm payments, providing complete transparency into the transaction’s cost, asset, and destination.
Developers can access testing environments with mock APIs and wallets and support for batched settlements, layer-2 blockchains, and payment channels.
It proposes a foundational change to how internet services interact with money by presenting on-chain payments via HTTP.
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