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r402

Modular Rust SDK for the x402 payment protocol — client signing, server gating, and facilitator settlement over HTTP 402.

What is r402?​

r402 is a comprehensive Rust implementation of the x402 protocol. It provides everything you need to build payment-gated HTTP services:

  • Server middleware — protect any Axum route with crypto payment requirements.
  • Client middleware — automatically sign and attach payments to outgoing requests.
  • Facilitator client — verify and settle payments on-chain.

Crates​

CrateDescription
r402Core library — protocol types, scheme traits, facilitator abstractions, hook system
r402-evmEVM (EIP-155) — ERC-3009 transfer authorization, multi-signer management
r402-svmSolana (SVM) — SPL token transfers, program-derived addressing
r402-httpHTTP transport — Axum payment gate, reqwest client middleware, facilitator client

Quick Start​

cargo add r402 r402-evm r402-http

Protect a Route (Server)​

use alloy_primitives::address;
use axum::{Router, routing::get};
use r402_evm::{Eip155Exact, USDC};
use r402_http::server::X402Middleware;

let x402 = X402Middleware::new("https://facilitator.example.com");

let app = Router::new().route(
    "/paid-content",
    get(handler).layer(
        x402.with_price_tag(Eip155Exact::price_tag(
            address!("0xYourPayToAddress"),
            USDC::base().amount(1_000_000u64), // 1 USDC
        ))
    ),
);

Send Payments (Client)​

use alloy_signer_local::PrivateKeySigner;
use r402_evm::Eip155ExactClient;
use r402_http::client::{ReqwestWithPayments, ReqwestWithPaymentsBuild, X402Client};
use std::sync::Arc;

let signer = Arc::new("0x…".parse::<PrivateKeySigner>()?);
let x402 = X402Client::new().register(Eip155ExactClient::new(signer));

let client = reqwest::Client::new()
    .with_payments(x402)
    .build();

let res = client.get("https://api.example.com/paid").send().await?;

Design Highlights​

AspectDetail
Built-in chains44 (42 EVM + 2 Solana)
Permit2Dual path — ERC-3009 + x402Permit2Proxy
Lifecycle hooksFacilitatorHooks + ClientHooks
Zero async_traitPure RPITIT, no trait-object overhead
EditionRust 2024

Feature Flags​

Crateserverclientfacilitatortelemetry
r402-httpAxum payment gateReqwest middlewareHTTP facilitator clienttracing spans
r402-evmPrice tag generationEIP-712 / EIP-3009 signingOn-chain verify & settletracing spans
r402-svmPrice tag generationSPL token signingOn-chain verify & settletracing spans

Source Code​