x402-foundation/x402

x402 is a payments protocol that enables HTTP-based transactions on the internet.

The protocol addresses the problem of integrating payments into web services by building directly on HTTP semantics. Rather than requiring separate payment infrastructure or proprietary channels, x402 extends HTTP with payment-related headers and status codes, allowing servers to request payment and clients to fulfill those requests within the standard HTTP request-response cycle. This approach treats payment as a first-class concern of the web protocol itself, similar to how HTTP handles authentication and caching.

Developers should consider x402 for projects that need to monetize API access, gate content behind micropayments, or build services where payment flows naturally into the HTTP interaction. The protocol suits scenarios where lightweight, standards-based payment integration is preferable to bolting on external payment processors. It works best for services that want payment semantics embedded in the transport layer rather than handled separately at the application level.

The project shows active development with regular commits and ongoing refinement of the protocol specification. The codebase maintains focus on the core HTTP-based payment mechanism without scope creep into unrelated concerns. Documentation and examples are present to guide implementers, though the project remains in active evolution as the protocol matures.