Introduction

ArcPay

Four ways to get paid. One URL.

The Stripe of USDC on Arc — for humans and AI agents. arcpay.finance/@you accepts tips, subscriptions, content paywalls, and pay-per-call API credits. 2% protocol fee, 0.5s settlement, native USDC gas.

The four primitives

  • Tips — one-time USDC with a message. Chrome extension injects a ⚡ Tip button into every tweet on X.
  • Subscriptions — monthly/yearly with per-second accrual and auto-prorated refund on cancel. 2% fee vs Patreon 10%.
  • Content paywall — gate articles, videos, courses with USDC. Buyer pays once, access is an on-chain receipt.
  • Pay-per-call — x402-compatible metered billing. batchPay prepays N inference credits in one on-chain transaction. SDK auto-signs each request. Server verifies callId on-chain.

All four share one UsernameRegistry — creators claim a handle once, use it everywhere.

Why Arc

Existing stablecoin chainsArc
Gas tokenSeparate (ETH / SOL / MATIC)USDC native
Finality13 s – 12 min~0.5 s
Cost per tx$0.01 – $5+~$0.0001
RegulatoryVariesCircle-backed, institutional-ready

Install

npm install @wanggang22/arcpay-sdk
# or
pip install arcpay

Send your first tip

import { ArcPayClient } from '@wanggang22/arcpay-sdk';
 
const client = new ArcPayClient({
  network: 'arc',
  privateKey: process.env.PRIVATE_KEY,
});
 
await client.tips.send({
  username: 'alice',
  amount: '0.005',
  message: 'Great post!',
});

Real USDC moves on-chain. No Stripe setup, no KYC, no $0.30 minimum per transaction.

Prepay N API calls (AI agents)

// One on-chain tx prepays 100 credits
await client.api.batchPay('alice', 'summarize-paper', 100);
 
// Each call consumes one credit:
//   const sig = await wallet.signMessage('arcpay-call:' + callId);
//   fetch(endpointUrl, { body: JSON.stringify({ callId, signature: sig, endpointId, input }) });

Server verifies callId + signature on-chain, consumes one credit, returns the response.

Fee model

2% per transaction (vs Stripe 2.9% + $0.30, Patreon 8–12%, Gumroad 10%). Protocol fee is capped at 10% and currently set to 2% for all modules.

Scaffold a project

npx create-arc-app my-app

Pick from 5 templates: creator tip page · subscription platform · content paywall · paid API (x402) · agent payment gateway.

Next

  • Read the Quick Start — ship your first payment flow in five minutes.
  • Explore Concepts — the four modes and the registry.
  • Browse SDK Reference — every export, every method.
  • See Templates — working starter projects.

Links

Quick Start