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Install @b3dotfun/anyspend-x402 package

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What is AnySpend x402?

AnySpend x402 is B3’s implementation of the x402 payment protocol that enables instant, automatic cryptocurrency payments directly over HTTP. Unlike traditional x402 facilitators that only support USDC, AnySpend allows you to pay with any token while resource servers receive any token they prefer. The x402 protocol modernizes the HTTP 402 Payment Required status code, turning it into a practical solution for machine-to-machine micropayments, paywalled APIs, and autonomous agent interactions.

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For Buyers (Payers)

Pay for paywalled resources using any cryptocurrency you hold:
  • Pay with any token: Use ETH, DAI, or any ERC-20 token - not just USDC
  • Standard protocol: Works with any x402-enabled service using standard HTTP
  • No manual swaps: AnySpend automatically converts your token to what the seller needs
  • Simple integration: One SDK works across all x402 services
Use Cases:
  • Access premium APIs and AI agent services
  • Pay for computational resources and data feeds
  • Enable autonomous agent-to-agent payments
  • Consume paywalled content programmatically

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For Sellers (Resource Servers)

Accept payments in USDC while your customers pay with their preferred token:
  • Receive USDC: Get paid in USDC regardless of what token the customer uses
  • Express middleware: Add payments to your API with just a few lines of code
  • No blockchain infrastructure: AnySpend handles all on-chain complexity
  • Instant settlement: Payments are verified and settled automatically
Use Cases:
  • Monetize premium APIs and data services
  • Build paid AI agent workflows
  • Create paywalled content and tools
  • Accept crypto payments without crypto expertise

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Quick Start

Choose your path:

I want to pay for services

For Buyers: Learn how to use the x402 client SDK to pay for paywalled resources with any token

I want to accept payments

For Sellers: Add the Express middleware to your API and start accepting multi-token payments

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How It Works

1

Client Requests Resource

User’s application makes a standard HTTP request to your API
2

Payment Required

Your API returns 402 Payment Required with payment details
3

Token Preference

Client specifies their preferred payment token (ETH, DAI, etc.)
4

AnySpend Quotes

AnySpend calculates the equivalent amount in the client’s chosen token
5

Client Signs Payment

User signs a cryptographic authorization for their token
6

Automatic Settlement

AnySpend swaps the token to USDC and settles to your wallet
7

Resource Delivered

Your API receives payment confirmation and returns the requested resource

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Key Differentiators

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Multi-Token Support

Standard x402: Resource servers and clients must both use USDC AnySpend x402: Clients pay with any token they hold. AnySpend handles the conversion. 
Client pays 0.0003 ETH → AnySpend swaps to 1 USDC → Seller receives 1 USDC

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No Infrastructure Required

Resource servers don’t need to:
  • Run blockchain nodes
  • Manage wallets or private keys
  • Handle token swaps or bridging
  • Monitor transaction status
AnySpend’s facilitator handles all blockchain operations and provides simple HTTP endpoints for verification and settlement.

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Standard Protocol Compliance

Clients using AnySpend have zero awareness they’re using a special facilitator. The entire flow uses standard x402 protocol messages - the multi-token magic happens transparently on the resource server side through middleware.

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Package Delivery

AnySpend x402 consists of two packages:

Server SDK

@b3dotfun/anyspend-x402Universal server middleware supporting Express, Next.js, and Hono for resource servers to easily accept multi-token payments

Client SDK

anyspend-x402-clientPlatform-agnostic TypeScript SDK for clients to make payments with signature helpers

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Powered by AnySpend Facilitator

All x402 payments are processed through the AnySpend Facilitator - a production-grade payment infrastructure that handles:
  • ✅ Multi-token support across 19+ blockchain networks
  • ✅ Automatic token swaps and cross-chain routing
  • ✅ Gasless payments for users
  • ✅ Standards-compliant x402 implementation
  • ✅ Drop-in replacement for any x402 facilitator
Production Endpoint: https://mainnet.anyspend.com/x402

Learn More About the Facilitator

Discover the full capabilities, API endpoints, and architecture of the AnySpend Facilitator