Glossary
A
Account A user profile in the 402x system. Unlike traditional platforms, 402x supports accountless payments where users can transact without creating an account.
API (Application Programming Interface) A set of endpoints and protocols that allow software applications to communicate with each other. In 402x, APIs can be monetized per-request.
API Key A secret token used to authenticate requests to the 402x API. Format: sk_live_... for production, sk_test_... for sandbox.
B
Base L2 (Layer 2) The Ethereum Layer 2 blockchain network used by 402x for fast, low-cost transactions. Built by Coinbase, it provides ~2 second finality and sub-cent transaction fees.
Blockchain A distributed ledger technology that records transactions across many computers. 402x uses Base L2 for payment settlement.
Bug Bounty A program that rewards security researchers for finding and responsibly disclosing vulnerabilities in 402x systems.
C
Confirmation The process of verifying a blockchain transaction. One confirmation means the transaction is included in a block; more confirmations increase security.
Consensus Agreement among network participants about the state of the blockchain. Ensures transaction validity and prevents double-spending.
CRUD (Create, Read, Update, Delete) Basic operations for managing data. 402x APIs support full CRUD operations for products, payments, and settings.
D
Dashboard The web interface at dashboard.402x.io for managing payments, analytics, and settings.
DDoS (Distributed Denial of Service) A cyber attack that overwhelms a system with traffic. 402x includes protection against DDoS attacks.
Dynamic Pricing Pricing that changes based on factors like demand, time, user behavior, or other conditions.
E
Endpoint A specific URL path in an API that performs a particular function. Example: POST /api/payments creates a new payment.
Escrow A financial arrangement where funds are held by a third party until conditions are met. 402x uses smart contract escrow for high-value transactions.
Ethereum The blockchain platform that Base L2 is built on. Provides security and finality guarantees.
F
Finality The point at which a transaction is considered irreversible. On Base L2, finality occurs in approximately 2 seconds.
Fraud Detection Automated systems that identify suspicious payment patterns and potential fraud attempts.
Fiat Traditional government-issued currency (USD, EUR, etc.) as opposed to cryptocurrency.
G
Gas The fee required to execute transactions on Ethereum. Base L2 has significantly lower gas costs than Ethereum mainnet (~$0.001 vs $5-50).
Gateway An entry point or interface between different systems. 402x acts as a payment gateway for web services.
H
Hash A cryptographic fingerprint of data. Transaction hashes uniquely identify blockchain transactions. Example: 0x8f4e2a1b...
HMAC (Hash-based Message Authentication Code) A cryptographic method for verifying message integrity and authenticity. Used in webhook signature verification.
HTTP 402 Payment Required An HTTP status code indicating that payment is required to access a resource. 402x operationalizes this status code.
I
Invoice A payment request with specific terms (amount, recipient, expiration). Each invoice has a unique ID like inv_abc123.
Idempotency The property that an operation can be performed multiple times with the same result. 402x APIs use idempotency keys to prevent duplicate charges.
J
JSON (JavaScript Object Notation) A lightweight data format used by 402x APIs for request and response bodies.
JWT (JSON Web Token) A compact, URL-safe means of representing claims between parties. Sometimes used for authentication.
K
KYC (Know Your Customer) Identity verification processes required by financial regulations. 402x implements risk-based KYC for high-value transactions.
Key Pair A public key and private key used in cryptographic operations. Wallets use key pairs to sign transactions.
L
Layer 2 (L2) A blockchain network built on top of a main blockchain (Layer 1) to improve scalability and reduce costs. Base is an Ethereum L2.
Latency The time delay between a request and response. 402x targets <100ms payment verification latency.
M
Mainnet The primary blockchain network where real transactions occur (vs. testnet for development).
Merchant A business or individual accepting payments through 402x.
Metadata Additional custom data attached to payments or products. Useful for tracking and organization.
Micropayment A very small payment, typically under $1. 402x is optimized for micropayments down to $0.01 or less.
Middleware Software that sits between an application and services, adding functionality. 402x provides middleware for payment processing.
N
Nonce A random number used once to prevent replay attacks. Each payment request includes a unique nonce.
Non-custodial A system where users maintain control of their private keys and funds, rather than trusting a third party.
O
OAuth An authorization framework. 402x supports OAuth for third-party integrations.
On-chain Transactions recorded on the blockchain, as opposed to off-chain or layer-2 solutions.
OpenAPI A specification for describing REST APIs. 402x provides OpenAPI documentation.
P
Paywall A system that restricts access to content until payment is made. 402x Paywalls enable instant micropayment-based access.
PCI DSS (Payment Card Industry Data Security Standard) Security standards for handling credit card information. 402x avoids credit cards, using crypto instead.
Private Key A secret cryptographic key that allows signing transactions. Must be kept secure.
Protocol A set of rules governing how data is transmitted. The x402 Protocol defines how payments are requested and verified.
Public Key A cryptographic key that can be shared publicly. Derived from a private key, used to verify signatures.
Q
QR Code A square barcode that can encode payment information for easy scanning.
R
Rate Limit Restrictions on how many requests can be made in a time period. Prevents abuse and ensures fair usage.
Refund Returning payment to the original payer. 402x supports configurable refund windows.
REST (Representational State Transfer) An architectural style for APIs. 402x uses RESTful APIs.
RPC (Remote Procedure Call) A protocol for executing functions on remote servers. Used for blockchain interactions.
S
Sandbox A testing environment that mimics production without real money or blockchain transactions.
SDK (Software Development Kit) A collection of tools, libraries, and documentation for building applications. 402x provides SDKs for JavaScript, Python, and more.
Settlement The final transfer of funds from payer to recipient. On-chain settlement is recorded on the blockchain.
Signature A cryptographic proof that a message was created by the holder of a private key.
Smart Contract Self-executing code on a blockchain. 402x uses smart contracts for payment processing and escrow.
Stablecoin A cryptocurrency designed to maintain a stable value, typically pegged to fiat currency. 402x primarily uses USDC.
T
Testnet A blockchain network for testing that uses fake currency. Used in 402x sandbox environment.
Throughput The number of transactions processed per second. 402x targets 1000+ payments/second.
Token In cryptocurrency, a digital asset on a blockchain. Also refers to authentication tokens.
Transaction A recorded transfer of value on the blockchain.
TLS (Transport Layer Security) Encryption protocol for secure communication over the internet. All 402x APIs use TLS 1.3.
U
USDC (USD Coin) A stablecoin pegged 1:1 to the US Dollar. Primary currency for 402x transactions.
UUID (Universally Unique Identifier) A 128-bit identifier guaranteed to be unique. Used for invoice IDs, payment IDs, etc.
V
Validator A node that confirms and validates blockchain transactions.
Velocity The rate of transactions. High velocity can trigger fraud detection.
W
Wallet Software or hardware that stores private keys and manages cryptocurrency.
Webhook An HTTP callback that sends real-time notifications when events occur. 402x sends webhooks for payment events.
Whitelist A list of approved addresses, IPs, or entities. Used for access control.
X
x402 Protocol The open payment protocol developed by Coinbase that enables instant, trustless micropayments across the internet.
Common Abbreviations
| Abbreviation | Meaning |
|---|---|
| AML | Anti-Money Laundering |
| API | Application Programming Interface |
| DApp | Decentralized Application |
| DDoS | Distributed Denial of Service |
| EOA | Externally Owned Account |
| ERC-20 | Ethereum Request for Comment 20 (token standard) |
| ETH | Ether (Ethereum's native currency) |
| GDPR | General Data Protection Regulation |
| GUI | Graphical User Interface |
| HTTP | Hypertext Transfer Protocol |
| HTTPS | HTTP Secure |
| JSON | JavaScript Object Notation |
| JWT | JSON Web Token |
| KYC | Know Your Customer |
| L1 | Layer 1 (main blockchain) |
| L2 | Layer 2 (scaling solution) |
| MEV | Maximal Extractable Value |
| P2P | Peer-to-Peer |
| PII | Personally Identifiable Information |
| REST | Representational State Transfer |
| SDK | Software Development Kit |
| TLS | Transport Layer Security |
| TX | Transaction |
| UI | User Interface |
| URL | Uniform Resource Locator |
| USDC | USD Coin |
| UX | User Experience |
| WAF | Web Application Firewall |
Payment States
| State | Description |
|---|---|
| Created | Payment invoice generated |
| Pending | Awaiting user payment |
| Submitted | Transaction sent to blockchain |
| Confirming | Waiting for block confirmations |
| Confirmed | Payment successful and verified |
| Failed | Transaction failed |
| Expired | Payment window exceeded |
| Refunded | Funds returned to payer |
| Disputed | Payment under dispute review |
Error Codes
| Code | Meaning |
|---|---|
| 400 | Bad Request - Invalid parameters |
| 401 | Unauthorized - Invalid API key |
| 402 | Payment Required |
| 403 | Forbidden - Insufficient permissions |
| 404 | Not Found - Resource doesn't exist |
| 429 | Too Many Requests - Rate limited |
| 500 | Internal Server Error |
| 503 | Service Unavailable |
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