| title: x402 Protocol Specification | |
| emoji: 💳 | |
| colorFrom: green | |
| colorTo: gray | |
| sdk: static | |
| sdk_version: "" | |
| app_file: README.md | |
| pinned: false | |
| license: mit | |
| # x402 Protocol Specification | |
| HTTP 402 Payment Required for AI agent micropayments. | |
| ## Overview | |
| x402 is the production implementation of HTTP 402 (reserved since 1998) for the autonomous agent economy. It enables machine-to-machine micropayments over USDC on Solana. | |
| ## How It Works | |
| 1. Agent requests a protected resource → HTTP 402 with payment challenge | |
| 2. Agent parses challenge, submits USDC payment on Solana | |
| 3. Gateway confirms settlement (~2-3 Solana slots) | |
| 4. Protected resource is returned | |
| Total round trip: < 3 seconds. No humans. No redirects. No API keys. | |
| ## Specification | |
| **Status**: v0.2.0 (active) | |
| - [Full docs](https://greensol.me/nullstate/docs/protocols/x402) | |
| - [Source code](https://github.com/nullstate/nullstate) | |
| - [Live gateway](https://greensol.me/nullstate) | |
| ## Implementations | |
| | Implementation | Language | Status | | |
| |--------------|----------|--------| | |
| | NullState Gateway | Python | Production | | |
| | Coinbase AgentKit | TypeScript | Beta | | |
| | AEON Protocol | Rust | Beta | | |
| ## License | |
| MIT — do whatever you want. | |