Exact

The exact scheme is a fixed-price payment scheme. The seller advertises one amount, the buyer signs for that exact amount, and the facilitator settles that payment for the request. Use exact when the final charge is known before the response is generated, such as a fixed-price API call, file download, or gated page.

Server Setup

TypeScript
Go
Python

import { HTTPFacilitatorClient } from "@x402/core/server";
import { paymentMiddleware, x402ResourceServer } from "@x402/express";
import { ExactEvmScheme } from "@x402/evm/exact/server";
import { ExactSvmScheme } from "@x402/svm/exact/server";

const facilitatorClient = new HTTPFacilitatorClient({
  url: "https://x402.org/facilitator",
});

const resourceServer = new x402ResourceServer(facilitatorClient)
  .register("eip155:84532", new ExactEvmScheme())
  .register("solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1", new ExactSvmScheme());

app.use(
  paymentMiddleware(
    {
      "GET /weather": {
        accepts: [
          {
            scheme: "exact",
            price: "$0.001",
            network: "eip155:84532",
            payTo: "0xYourAddress",
          },
          {
            scheme: "exact",
            price: "$0.001",
            network: "solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1",
            payTo: "YourSolanaAddress",
          },
        ],
        description: "Weather data",
        mimeType: "application/json",
      },
    },
    resourceServer,
  ),
);

routes := x402http.RoutesConfig{
    "GET /weather": {
        Accepts: x402http.PaymentOptions{
            {
                Scheme:  "exact",
                Price:   "$0.001",
                Network: "eip155:84532",
                PayTo:   "0xYourAddress",
            },
            {
                Scheme:  "exact",
                Price:   "$0.001",
                Network: "solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1",
                PayTo:   "YourSolanaAddress",
            },
        },
        Description: "Weather data",
        MimeType:    "application/json",
    },
}

handler := nethttpmw.X402Payment(nethttpmw.Config{
    Routes:      routes,
    Facilitator: facilitatorClient,
    Schemes: []nethttpmw.SchemeConfig{
        {Network: x402.Network("eip155:84532"), Server: exactevm.NewExactEvmScheme()},
        {Network: x402.Network("solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1"), Server: exactsvm.NewExactSvmScheme()},
    },
})(mux)

from fastapi import FastAPI

from x402.http import FacilitatorConfig, HTTPFacilitatorClient, PaymentOption
from x402.http.middleware.fastapi import PaymentMiddlewareASGI
from x402.http.types import RouteConfig
from x402.mechanisms.evm.exact import ExactEvmServerScheme
from x402.mechanisms.svm.exact import ExactSvmServerScheme
from x402.server import x402ResourceServer

app = FastAPI()
facilitator = HTTPFacilitatorClient(FacilitatorConfig(url="https://x402.org/facilitator"))

server = x402ResourceServer(facilitator)
server.register("eip155:84532", ExactEvmServerScheme())
server.register("solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1", ExactSvmServerScheme())

routes = {
    "GET /weather": RouteConfig(
        accepts=[
            PaymentOption(
                scheme="exact",
                price="$0.001",
                network="eip155:84532",
                pay_to="0xYourAddress",
            ),
            PaymentOption(
                scheme="exact",
                price="$0.001",
                network="solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1",
                pay_to="YourSolanaAddress",
            ),
        ],
        description="Weather data",
        mime_type="application/json",
    ),
}

app.add_middleware(PaymentMiddlewareASGI, routes=routes, server=server)

Client Setup

TypeScript
Go
Python

import { x402Client } from "@x402/core/client";
import { ExactEvmScheme } from "@x402/evm/exact/client";
import { ExactSvmScheme } from "@x402/svm/exact/client";
import { createKeyPairSignerFromBytes } from "@solana/kit";
import { base58 } from "@scure/base";
import { privateKeyToAccount } from "viem/accounts";

const evmSigner = privateKeyToAccount(process.env.EVM_PRIVATE_KEY as `0x${string}`);
const svmSigner = await createKeyPairSignerFromBytes(
  base58.decode(process.env.SVM_PRIVATE_KEY!),
);

const client = new x402Client();
client.register("eip155:*", new ExactEvmScheme(evmSigner));
client.register("solana:*", new ExactSvmScheme(svmSigner));

import (
    x402 "github.com/x402-foundation/x402/go/v2"
    exactevm "github.com/x402-foundation/x402/go/v2/mechanisms/evm/exact/client"
    exactsvm "github.com/x402-foundation/x402/go/v2/mechanisms/svm/exact/client"
    evmsigners "github.com/x402-foundation/x402/go/v2/signers/evm"
    svmsigners "github.com/x402-foundation/x402/go/v2/signers/svm"
)

evmSigner, err := evmsigners.NewClientSignerFromPrivateKey(os.Getenv("EVM_PRIVATE_KEY"))
if err != nil {
    log.Fatal(err)
}

svmSigner, err := svmsigners.NewClientSignerFromPrivateKey(os.Getenv("SVM_PRIVATE_KEY"))
if err != nil {
    log.Fatal(err)
}

x402Client := x402.Newx402Client().
    Register("eip155:*", exactevm.NewExactEvmScheme(evmSigner, nil)).
    Register("solana:*", exactsvm.NewExactSvmScheme(svmSigner))

import os

from eth_account import Account

from x402 import x402Client
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client
from x402.mechanisms.svm import KeypairSigner
from x402.mechanisms.svm.exact.register import register_exact_svm_client

client = x402Client()

account = Account.from_key(os.getenv("EVM_PRIVATE_KEY"))
register_exact_evm_client(client, EthAccountSigner(account))

svm_signer = KeypairSigner.from_base58(os.getenv("SVM_PRIVATE_KEY"))
register_exact_svm_client(client, svm_signer)

Network Implementations

The exact scheme has network specifications for EVM, SVM, AVM, Stellar, Aptos, Hedera, TON, Cardano, Keeta, and Sui.

SVM Smart Wallet Support

By default, the SVM facilitator only accepts transactions from standard (EOA) wallets using static instruction-layout validation. To also accept payments from Solana smart wallets (Squads, Swig, SPL Governance, etc.), enable simulation-based verification when constructing ExactSvmScheme on your facilitator:

import { ExactSvmScheme } from "@x402/svm/exact/facilitator";
import { toFacilitatorSvmSigner } from "@x402/svm";

const svmSigner = toFacilitatorSvmSigner(svmAccount);

facilitator.register(
  "solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1",
  new ExactSvmScheme(svmSigner, undefined, {
    enableSmartWalletVerification: true,
  }),
);

When enableSmartWalletVerification is enabled, transactions that fail static validation (because they contain smart wallet program instructions) are re-verified by simulating the transaction and inspecting CPI inner instructions for a valid TransferChecked. Only programs in the built-in allowlist (Squads Multisig v4, Squads Smart Account, Swig, SPL Governance, Metaplex Core, Lighthouse) can reach this path.

toFacilitatorSvmSigner() is required when enabling smart wallet verification — it provides the simulateTransactionWithInnerInstructions, getConfirmedTransactionInnerInstructions, getTokenAccountBalance, and fetchAddressLookupTables methods needed for simulation-based verification.

Additional options:

Option	Type	Default	Description
`enableSmartWalletVerification`	`boolean`	`false`	Enable simulation-based verification for smart wallet transactions.
`smartWalletMaxComputeUnits`	`number`	`400000`	Maximum compute units allowed for smart wallet transactions.
`smartWalletMaxPriorityFeeMicroLamports`	`number`	`50000`	Maximum priority fee in microlamports for smart wallet transactions.
`smartWalletAllowedPrograms`	`string[]`	Built-in list	Allowed smart wallet program addresses. Only transactions invoking a program in this list reach simulation-based verification.

EVM Transfer Methods

The EVM implementation supports two transfer methods:

Method	Description
`eip3009`	Uses token-native `transferWithAuthorization`, commonly for USDC. This is the default when supported.
`permit2`	Uses Uniswap Permit2 plus the x402 exact proxy, so it can support ERC-20 tokens without EIP-3009.

Permit2 may require a one-time approval. The gas sponsoring extensions can let the facilitator handle that approval path for compatible tokens.

Server Setup

Client Setup

Network Implementations

SVM Smart Wallet Support

EVM Transfer Methods

Examples

Specs

See Also

​Server Setup

​Client Setup

​Network Implementations

​SVM Smart Wallet Support

​EVM Transfer Methods

​Examples

​Specs

​See Also

Server Setup

Client Setup

Network Implementations

SVM Smart Wallet Support

EVM Transfer Methods

Examples

Specs

See Also