B402

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B402

B402 is Binance's implementation of the x402 payment protocol on BNB Smart Chain. It enables instant, automatic stablecoin payments directly over HTTP — services charge buyers (human users or autonomous AI agents) per request, settled on-chain in seconds, with gas sponsored by B402. The recommended /papi/v2/b402/* API conforms to the x402 v2 specification; a V1 API (/papi/v1/b402/*) is also available for legacy clients.

Who B402 is for

• Sellers — API providers, paywall operators, AI tool authors, and microservice owners who want to monetize HTTP endpoints per request without building wallets, billing, or subscription infrastructure.
• Buyers — AI agents, dApps, and HTTP clients that pay for resources autonomously by signing EIP-712 authorizations. Buyers do not run wallets or hold gas — they sign off-chain and B402 executes the on-chain transfer.

Use cases

• Per-request API billing — charge fractions of a cent per call without managing API keys or invoices.
• AI agent payments — let autonomous agents pay for tools, data, and inference without human-in-the-loop credentials.
• Paywalled content — gate articles, downloads, or premium endpoints with HTTP 402.
• Microservice metering — charge internal or external consumers per call against a shared contract.
• Discovery of paid endpoints — be found by AI agents via B402 Bazaar without manual onboarding.

How It Works

The x402 protocol leverages the HTTP 402 Payment Required status code to create a standardized payment flow for web resources:

1. A client requests a paid resource from the seller.
2. The seller responds with HTTP 402 and includes payment requirements (token, amount, recipient address, and the addresses needed to construct an EIP-712 signature) in the response body.
3. The buyer signs an EIP-712 authorization off-chain (no on-chain transaction needed from the buyer).
4. The buyer resubmits the request with the signed payment attached.
5. The seller calls B402 to verify the signature and then settle the payment on-chain.
6. B402 sponsors the gas and executes the token transfer directly from buyer to seller.
7. The seller delivers the paid resource.

For the full sequence diagram and step-by-step walkthrough, see Typical integration flow.

Key roles

Role	Description
Buyer (AI agent / user)	The payer who signs an EIP-712 authorization off-chain to approve the token transfer. Can be a human user or an autonomous AI agent.
Seller (merchant / developer)	Provides paid APIs or services. Integrates B402 via HTTP. Forwards the buyer's signed payment to the B402 facilitator for verification and execution.
Facilitator (B402)	Verifies signatures off-chain (/verify), then sponsors gas and executes the on-chain token transfer (/settle). All token transfers occur strictly peer-to-peer on the public blockchain from the buyer's wallet directly to the merchant's wallet.

Key features

• Stateless — no sessions, accounts, or held balances. Each request is its own transaction.
• HTTP-native — payments flow through standard request/response with the 402 status code. Works with any HTTP server, framework, or client.
• Gas-sponsored — sellers don't need BNB to operate. B402 pays the gas for every settle.
• Multiple payment methods — eip3009 for native EIP-3009 tokens (U, USD1) and permit2-exact / permit2-upto for any ERC-20 (USDC, USDT, etc.).
• Discoverable — opt your endpoints into B402 Bazaar for AI-agent discovery simply by attaching metadata on settle.
• CDP wire-shape compatible — the V2 PaymentPayload and Bazaar metadata blob match Coinbase's x402 spec field-for-field, so client libraries built for CDP work against B402 with one URL change.

Supported payment methods

Token	Contract (BSC Mainnet)	eip3009	permit2-exact	permit2-upto
U	0xcE24439F2D9C6a2289F741120FE202248B666666	✅	✅	✅
USD1	0x8d0D000Ee44948FC98c9B98A4FA4921476f08B0d	✅	✅	✅
USDT	0x55d398326f99059fF775485246999027B3197955	—	✅	✅
USDC	0x8AC76a51cc950d9822D68b83fE1Ad97B32Cd580d	—	✅	✅

Method	Description
eip3009	EIP-3009 native transferWithAuthorization. Only available for tokens with built-in EIP-3009 support (U, USD1).
permit2-exact	Permit2 exact-amount transfer. Works with any ERC-20 token.
permit2-upto	Permit2 up-to-amount transfer (pay-as-you-go). Works with any ERC-20 token.

Current status

B402 is live on BNB Smart Chain (BSC) Testnet for external partner onboarding. Production (BSC Mainnet) access is granted on request — apply here to get your API credentials. See Environments and API base URLs for endpoint details. Expansion to other EVM-compatible networks is planned.

What to read next

• Quick Start — step-by-step guide to your first integration.
• Typical integration flow — full sequence diagram and per-step explanation of the protocol.
• Integration Guideline — production prerequisites, rate limits, and security best practices.
• B402 Bazaar — make your endpoint discoverable to AI agents.
• Open APIs V2 — detailed API reference for /supported, /verify, and /settle (x402 v2 spec-conformant).
• Permit2 Signing Guide — the EIP-712 typed data shape for Permit2 signatures, with viem and ethers.js v6 reference implementations.

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Disclaimer

This documentation describes Binance x402 (B402), a developer-facing technical service that supports verification of user-signed x402-compatible payment payloads and submission of corresponding on-chain transactions on supported blockchain networks.

Binance x402 (B402) is provided as technical infrastructure and software tooling only. It is not intended to constitute, and should not be construed as, any of the following:

• a bank account, deposit, stored-value facility, e-money product, or custodial wallet;
• a payment account, payment instrument, remittance, money transmission, or funds transfer service;
• brokerage, exchange, dealing, clearing, settlement assurance, or other regulated financial service;
• investment, legal, tax, accounting, or regulatory advice;
• an offer, invitation, solicitation, recommendation, or endorsement to buy, sell, hold, transfer, or use any digital asset, token, or network.

B402 does not take possession, custody, or control of user funds or payment tokens as part of the standard flow described in this documentation. In the supported integration model, digital assets move directly on-chain between addresses designated by the user and the merchant or service provider. B402's role is limited to technical functions such as message validation, signature verification, transaction submission, and related API support on supported networks.

Use of B402 does not relieve any developer, merchant, integrator, application provider, or other participant of its own responsibility to assess and comply with all applicable laws, rules, regulations, licensing, sanctions, tax, consumer protection, data protection, and disclosure obligations in each relevant jurisdiction. Each integrator remains solely responsible for:

• determining whether and how B402 may be used in its product or service;
• ensuring that all required notices, disclosures, consents, and terms are provided to end users;
• evaluating whether any activity involving digital assets, blockchain-based transfers, or service monetization may be regulated in applicable jurisdictions;
• implementing its own compliance, fraud prevention, transaction monitoring, screening, risk management, and customer support processes as required.

Blockchain networks, smart contracts, token standards, third-party wallets, signatures, RPC infrastructure, and related software involve operational, technical, and legal risks, including failed transactions, reversibility limitations, network congestion, software bugs, forks, validator or sequencer issues, smart contract vulnerabilities, signature misuse, incorrect addressing, and asset loss. On-chain transactions may be irreversible once confirmed. Binance x402 (B402) does not guarantee transaction success, network availability, confirmation times, compatibility, merchant outcomes, user solvency, or continued support for any blockchain, token, standard, or integration.

This documentation is provided for general informational and integration purposes only and may be updated, suspended, or withdrawn at any time. Access to or use of B402 may be subject to separate eligibility requirements, onboarding, contractual terms, technical restrictions, and jurisdictional limitations. Availability may differ by entity, user type, product configuration, and region.

To the extent permitted by applicable law, Binance x402 (B402) and its providers disclaim liability for indirect, incidental, consequential, special, exemplary, or punitive damages, and for losses arising from third-party acts or omissions, blockchain events, token issuer actions, smart contract behavior, wallet compromise, configuration errors, unsupported use cases, or user/integrator non-compliance.

You should obtain independent legal, regulatory, tax, and technical advice before deploying Binance x402 (B402) in production.