AnySpend x402 overview

Pay for paywalled APIs and services with any token using the x402 open payment protocol

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npm Package

Install @b3dotfun/anyspend-x402 package

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 compatible token (EIP-2612 or EIP-3009) 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.

For buyers (payers)

Pay for paywalled resources using any compatible token you hold:

Pay with compatible tokens: Use any token with EIP-2612 or EIP-3009 support for gasless payments
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

Token Compatibility Checker

Browse compatible tokens with EIP-2612 or EIP-3009 support across 19+ networks

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

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

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

Learn More

I want to accept payments

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

Learn More

How it works

Client Requests Resource

User's application makes a standard HTTP request to your API

Payment Required

Your API returns 402 Payment Required with payment details

Token Preference

Client specifies their preferred payment token (USDC, USDT, etc.)

AnySpend Quotes

AnySpend calculates the equivalent amount in the client's chosen token

Client Signs Payment

User signs a cryptographic authorization for their token

Automatic Settlement

AnySpend swaps the token to USDC and settles to your wallet

Resource Delivered

Your API receives payment confirmation and returns the requested resource

Key differentiators

Multi-token support

Standard x402: Resource servers and clients must both use USDC

AnySpend x402: Clients pay with any compatible token (EIP-2612 or EIP-3009 support required) they hold. AnySpend handles the conversion.

text
Client pays with DAI (EIP-2612) → AnySpend swaps to 1 USDC → Seller receives 1 USDC

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.

Standard protocol compliance

Clients using AnySpend don't need to know they're using a special facilitator. The flow uses standard x402 protocol messages, and the multi-token conversion happens on the resource server side through middleware.