B402

B402 is an on-chain developer-facing x402 transaction verification and submission service built on the x402 protocol (HTTP 402 Payment Required). It enables merchants and developers to integrate x402-compatible transaction flows through standard HTTP APIs — no smart-contract development needed. The recommended /papi/v2/b402/* API is conformant with the x402 v2 specification; a V1 API (/papi/v1/b402/*) is also available.

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) in the X-PAYMENT-REQUIREMENTS header.
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 submit 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.

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 x402 facilitator for execution amount verification.
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.

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.

Gas Sponsorship

B402 sponsors all gas fees for settlement transactions, so the merchant does not need to hold BNB for gas.

Current Status

B402 is live on BNB Smart Chain (BSC) Testnet for external partner onboarding. Production (BSC Mainnet) access is granted on request — see Environments and API base URLs. Expansion to other EVM-compatible networks is planned.

Next Steps

• Quick Start — Step-by-step guide to your first integration.
• Integration Guideline — Prerequisites, checklist, and best practices.
• Basics — Common request headers, response formats, request signing, and environments.
• Open APIs V2 — Detailed API reference for /supported, /verify, and /settle (x402 v2 spec-conformant).

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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.