Free x402 tools

Build, price, and debug x402 flows in your browser.

These tools are client-side only. Generate a v2 402 response, compare x402 pay-per-use economics, or decode Base64 payment headers without creating an account or sending payloads to a server.

PAYMENT-REQUIREDx402 example

402 Response Builder

Generate a client-side x402 v2 PAYMENT-REQUIRED response, Base64 header value, decoded JSON object, and retry curl shape.

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pricingpay per use API

x402 Pricing Calculator

Compare pay-per-use x402 API revenue against subscription or API-key pricing with dated fee assumptions you can edit.

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PAYMENT-SIGNATUREX-PAYMENT

Payment Header Decoder

Decode Base64 x402 PAYMENT-SIGNATURE, PAYMENT-REQUIRED, PAYMENT-RESPONSE, or legacy X-PAYMENT values entirely in the browser.

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Related reading

Use tools with the implementation guides

The HTTP 402 Flow

A step-by-step map of the x402 v2 request flow, including PAYMENT-REQUIRED, PAYMENT-SIGNATURE, and PAYMENT-RESPONSE.

Server Integration Guide

How to decide what to protect with x402, configure route requirements, choose a facilitator, and test paid API endpoints.

x402 Header Format

A field guide to x402 v2 PAYMENT-REQUIRED, PAYMENT-SIGNATURE, PAYMENT-RESPONSE, Base64 JSON values, and legacy X-PAYMENT migration.