Concepts

Concepts

Architecture

ArcPay is 6 contracts working together:

UsernameRegistry     → creator ID → payout address
    ↓
    ├── TipJar          → one-time payments
    ├── Subscriptions   → recurring payments
    ├── ContentPaywall  → per-item access
    └── PayPerCall      → x402 API billing
    ↑
ArcPayHub           → central directory (read-only)

Each module is independent but shares the single UsernameRegistry. Creators register once, use every module.

Native USDC on Arc

Arc treats USDC as native gas. That means:

  • msg.value IS USDC (not ETH-wrapped)
  • No approve() needed for USDC payments
  • Fees paid in USDC
  • Same 18-decimal precision as native currency

This is the opposite of ERC-20 USDC on other chains where you need a separate gas token.

The 4 payment modes

Tips

Lightweight one-time transfers with an optional message. Best for “buy me a coffee” or “thanks for the post” flows.

Subscriptions

Pre-paid recurring access. Subscriber pays N months upfront; time-based revenue accrual; prorated refund on cancel.

Key design: subscribers control cancel, creators control plan lifecycle. No stuck subscriptions.

Content Paywall

Pay-once-access-forever model for articles, videos, courses. Content ID is usually keccak256(ipfs_cid) or similar stable identifier.

Metadata lives off-chain (IPFS/Arweave/S3) — contract only stores the price and access records.

Pay-per-call (x402)

Every API request requires an on-chain payment. Server verifies the receipt before serving.

Compatible with the HTTP 402 specification: a failed call can return a 402 + payment instructions.

Protocol fee

2% of each payment goes to the protocol treasury. Capped at 10% in contract.

Creator receives the remaining 98% directly.

Username system

  • 3-32 chars, lowercase, [a-z0-9_-]
  • Unique, first-come-first-served
  • Owner can update payout address + metadata
  • Third-party verifiers can mark “verified” (e.g., Twitter/GitHub oracles)

What ArcPay is NOT

  • Not a custodial wallet (users keep their private keys or use Circle Wallets)
  • Not a yield protocol (yield-bearing USDC via USYC/Aave is planned v0.3)
  • Not a market (no bidding, no auctions)
  • Not a compliance product (Circle’s CPN does KYC/AML for institutions)
Quick StartSDK Reference