> ## Documentation Index > Fetch the complete documentation index at: https://docs.x402.org/llms.txt > Use this file to discover all available pages before exploring further. # Exact > Fixed-price x402 payments where the buyer authorizes exactly the advertised amount. 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 theme={null} 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, ), ); ``` ```go theme={null} 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) ``` ```python theme={null} 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="$0.001", network="solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1", pay_to="YourSolanaAddress", ), ], description="Weather data", mime_type="application/json", ), } app.add_middleware(PaymentMiddlewareASGI, routes=routes, server=server) ``` ### Client Setup ```typescript theme={null} import { x402Client } from "@x402/core/client"; import { ExactEvmScheme } from "@x402/evm/exact/client"; import { ExactSvmScheme } from "@x402/svm/exact/client"; import { createKeyPairSignerFromBytes } from "@solana/kit"; import { base58 } from "@scure/base"; import { privateKeyToAccount } from "viem/accounts"; const evmSigner = privateKeyToAccount(process.env.EVM_PRIVATE_KEY as `0x${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)); ``` ```go theme={null} 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)) ``` ```python theme={null} 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: ```typescript theme={null} 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. ### Examples * [TypeScript server example](https://github.com/x402-foundation/x402/tree/main/examples/typescript/servers/express) * [TypeScript client example](https://github.com/x402-foundation/x402/tree/main/examples/typescript/clients/fetch) * [Go server example](https://github.com/x402-foundation/x402/tree/main/examples/go/servers/nethttp) * [Go client example](https://github.com/x402-foundation/x402/tree/main/examples/go/clients/http) * [Python server example](https://github.com/x402-foundation/x402/tree/main/examples/python/servers/fastapi) * [Python client example](https://github.com/x402-foundation/x402/tree/main/examples/python/clients/requests) ### Specs * [`exact` spec](https://github.com/x402-foundation/x402/blob/main/specs/schemes/exact/scheme_exact.md) * [`exact` EVM spec](https://github.com/x402-foundation/x402/blob/main/specs/schemes/exact/scheme_exact_evm.md) * [`exact` SVM spec](https://github.com/x402-foundation/x402/blob/main/specs/schemes/exact/scheme_exact_svm.md) * [`exact` AVM spec](https://github.com/x402-foundation/x402/blob/main/specs/schemes/exact/scheme_exact_algo.md) * [`exact` Stellar spec](https://github.com/x402-foundation/x402/blob/main/specs/schemes/exact/scheme_exact_stellar.md) * [`exact` Aptos spec](https://github.com/x402-foundation/x402/blob/main/specs/schemes/exact/scheme_exact_aptos.md) * [`exact` Hedera spec](https://github.com/x402-foundation/x402/blob/main/specs/schemes/exact/scheme_exact_hedera.md) * [`exact` TON spec](https://github.com/x402-foundation/x402/blob/main/specs/schemes/exact/scheme_exact_ton.md) ### See Also * [Payment schemes overview](/schemes/overview) * [Upto](/schemes/upto) * [Batch settlement](/schemes/batch-settlement)