What is ArQPay?

ArQPay is a cryptocurrency payment processor that lets your customers pay invoices in crypto while you settle in stablecoins. It combines:

• A hosted payment widget — a self-contained <script> tag you embed on your checkout page.
• A REST API — for server-side quote creation, payment status checks, confirmation and webhook management.
• Smart-contract settlement — funds flow through audited on-chain contracts (PaymentProcessor, MerchantRegistry, TrustedForwarder, …) so custody and distribution are transparent and trust-minimized.

Who is it for?

Any merchant who wants to accept crypto without running their own infrastructure:

Use case	How ArQPay helps
Simple checkout	Embed the widget, done. No backend code needed.
Custom UX	Call the REST API from your own backend and build your own UI.
High-volume stores	Receive signed webhooks and reconcile payments programmatically.
Referral programs	Attach an affiliateId to any payment to share fees with affiliates.

Key concepts

Merchant

A merchant is identified by a merchant ID (a bytes32 hash, e.g. 0x…). Each merchant has:

• A recipient address — where settled funds are distributed.
• A set of supported chain IDs.
• An allowed origins list — the websites permitted to initiate payments (CORS-style protection).
• Optional webhook configuration for payment notifications.

Quote

Every payment starts with a quote: a server-computed snapshot of the exchange rate, fee and exact on-chain calldata, locked in for 5 minutes (quoteDeadline). The quote is cryptographically hashed (quoteHash) and validated on-chain, so the payer cannot tamper with amounts after quoting.

Payment lifecycle

pending → completed
   ↘
    failed
   ↘
    waiting_relayer   (gasless payments only)

• pending — quote created, awaiting the payer's transaction (or relay submission).
• waiting_relayer — gasless payment submitted, waiting for the relayer to broadcast.
• completed — on-chain execution verified, funds distributed.
• failed — execution reverted or confirmation failed.

Two payment modes

Mode	Who pays gas	Flow
Standard	The payer	Payer signs & broadcasts the swap transaction themselves.
Gasless	Nobody (borne/settled by the platform)	Payer signs two offline signatures; ArQPay's relayer submits the transaction. Requires an ERC-20 token supporting EIP-2612 permit.

Architecture overview

┌────────────────┐      ┌─────────────────────┐      ┌──────────────────┐
│  Your website  │ ───▶ │     ArQPay Host     │ ───▶ │   ArQPay Backend │
│  (checkout)    │      │  serves widget.js   │      │                  │
└────────────────┘      │  serves /api/*      │      └────────┬─────────┘
                         └─────────────────────┘               │
                                                                ▼
                                                      ┌──────────────────┐
                                                      │  Smart Contracts │
                                                      │  (EVM chains)    │
                                                      └──────────────────┘

• ArQPay Host — serves the payment widget assets and the API endpoints, so browser integrations work without CORS configuration.
• Backend — computes quotes, manages merchants, dispatches webhooks and runs the gasless relayer.
• Smart contracts — per-chain deployment of the payment processor suite; the backend verifies merchant registration on-chain before accepting quotes.

Where to go next

• Quick Start — take your first payment in under 10 minutes.
• Widget Integration — embed the widget on your site.
• Server-Side Integration — drive the API from your own backend.
• API Reference — full endpoint documentation.