L402
    Protocol
    OPEN PROTOCOL

    L402: native payments for
    MCP
    AI Agents
    APIs
    Data
    MCP

    A universal HTTP-based payment flow that enables direct monetization from anywhere. No browser needed.

    Any Payment Method

    Works out of the box with credit cards, bank rails and crypto.

    Simple Integration

    Built on HTTP 402 standard. Just a few lines of code to implement.

    AI-Ready

    Easiest way to give AI agents the ability to pay for services.

    SIMPLE PROTOCOL

    How L402 Works

    L402 mimics familiar browser payment flows using the HTTP 402 "Payment Required" standard.

    ServerClientPayment Gateway

    Client Requests Resource

    A client attempts to access a protected API resource that requires payment to use.

    L402 Flow: How It Works

    1) A client attempts to access a protected API resource that requires payment to use.

    2) Server responds with a 402 Payment Required status code and JSON containing available payment offers and methods for the client to choose from.

    3) Client contacts the payment gateway to request specific payment details for their chosen offer and preferred payment method.

    4) Gateway returns payment details needed for the transaction - such as a checkout URL, Lightning invoice, or ACH account information.

    5) Client completes the payment outside of the protocol using their selected payment method and the provided payment details.

    6) Once payment is confirmed, the payment gateway notifies the server that the payment has been received successfully.

    7) When the client requests the resource again, the server recognizes the completed payment and grants access to the protected resource.

    The entire flow uses standard HTTP semantics, making it compatible with any HTTP client - browsers, API clients, or AI agents. While the API, payment gateway, and server are shown as separate entities, with self-custodial methods they could be implemented as the same entity.

    COMPATIBILITY

    Payment Method Support

    L402 works with virtually any payment method, providing a unified interface for all transactions.

    Banking

    WireACHSEPA

    Credit Cards

    VisaMastercardAmex

    Cryptocurrencies

    BitcoinBaseSolana
    BENEFITS

    Key Features

    L402 delivers unique advantages for payment processing on the internet.

    Open Source

    Built for transparency and community contribution, allowing anyone to extend and improve.

    Universal Compatibility

    Works with every payment method from credit cards to crypto, Lightning, and stablecoins.

    Simple & HTTP-Based

    Built on standard HTTP status codes and headers, requiring minimal code to implement.

    AI-Agent Ready

    Designed specifically for machines to autonomously handle payments without friction.

    Perfect for Micropayments

    Ideal for pay-per-use APIs, metered content, or any small-value transactions.

    Secure By Design

    Built with security first, leveraging proven cryptographic methods for payment verification.

    Ready to implement L402?

    Get started with L402 today and enable seamless payment processing for your applications, APIs, and AI agents.