What is x402? | Payment Protocol for AI Agents on Solana

The HTTP 402 Status Code

HTTP 402 (Payment Required) has existed since 1997 but was never implemented—until now. x402 activates this dormant status code, enabling any API or web service to require payment before serving content. It's a universal standard for monetizing digital resources.

Why Solana for x402?

Solana's 400ms finality and $0.00025 transaction costs make it the perfect settlement layer for x402. Whether it's an AI agent making thousands of API calls or a user accessing premium content, Solana enables instant, low-cost payments that make micropayments economically viable. With native USDC support, x402 on Solana provides stable, predictable pricing for global services.

Powering the Agent Economy

AI agents need to transact autonomously—paying for APIs, buying data, and accessing services without human intervention. x402 makes this possible. An agent can request access to a paid resource, receive a 402 response with payment details, execute the payment on Solana, and receive the resource—all in milliseconds. This isn't theoretical: x402 transactions grew 10,000% in a month, with over 500,000 weekly transactions as developers build agent-first applications. The protocol enables agents to operate wallets, negotiate prices, and participate in markets independently.

A Growing Ecosystem

The x402 community spans 40+ partners building everything from client SDKs to payment facilitators. Major platforms like Cloudflare, AWS, and Anthropic support x402, while the ecosystem's $806M market cap reflects real adoption. Developers are creating MCP servers that connect AI models to x402 services, building payment infrastructure for agent marketplaces, and launching tools that make integration effortless. With active participation across Base, Solana, Polygon, and NEAR, x402 is becoming the standard for internet payments.

Real-World Use Cases

• →AI agents autonomously paying for API access, data feeds, and compute resources
• →Developer APIs monetized per-request without subscription complexity
• →Content creators charging micropayments for articles, images, or model inference
• →Agent marketplaces where autonomous buyers and sellers transact 24/7
• →Cross-chain services accepting payments on multiple networks