Free x402 tool

x402 Flow Simulator

Walk through the x402 exchange one state at a time. The simulator shows what the buyer sends, what the seller returns, and where facilitator verification and settlement fit.

Simulator

Protocol steps

Buyer

HTTP transcript

 
 
 
Payment object
 
 
 
 
 
Reference tools
 

This simulator teaches the sequence. For field-level reference work, use the
x402docs 402 Response Builder
and
Payment Header Decoder.

 
 
 
   
 
FAQ
 

Tool FAQ

 
 
 
Are the simulated headers valid payment headers?
 
No. They are readable educational examples that show shape and sequence. Use the official SDKs and x402docs tools for valid production payload construction and decoding.
 
 
Why does the simulator show a facilitator?
 
The official flow allows the seller to verify and settle directly or through a facilitator. The simulator shows the facilitator path because it is the common mental model for new builders.
 
 
What should I inspect when debugging x402?
 
Capture the status code, PAYMENT-REQUIRED challenge, selected scheme and network, PAYMENT-SIGNATURE retry, verification result, settlement result, and PAYMENT-RESPONSE metadata.
 
 
 
  
 
Sources used
 
     
  1.  x402 docs: Introduction 
    Defines x402 as an open payment standard for charging APIs and content directly over HTTP.
     
  2.  x402 docs: HTTP 402 
    Explains how x402 uses HTTP 402 to communicate payment requirements.
     
  3.  x402 docs: Facilitator 
    Defines facilitator responsibilities for payment verification and settlement.
     
  4.  x402 docs: Quickstart for Sellers 
    Official seller setup, package installation, testnet defaults, and payment middleware examples.
     
  5.  x402docs.com reference tools 
    Reference-style x402 tools for building 402 responses, pricing, and decoding payment headers.
     
    6.