Glossary

Key terms and definitions.

x402
Protocol for implementing HTTP 402 using blockchain payments.
Payment Challenge
A cryptographic token containing payment requirements (price, recipient, network, expiry).
Access Token
A JWT issued after payment verification for session-based access.
Payment Proof
Transaction hash and signature proving payment was made.
Verification
On-chain confirmation that payment exists and matches requirements.
Quota
Usage allocation for metered billing (e.g., API tokens, bytes).
Receipt
Proof of payment issued by the server after verification.
Middleware
Server-side code that handles payment challenges and verification.
EIP-1193
Standard Ethereum provider interface used by wallets.