MiniPay Integration

This skill covers building Mini Apps for MiniPay, the fastest growing non-custodial wallet in the Global South with ~18M wallet activations and 470M+ transactions across 66+ countries.

When to Use

• Building Mini Apps for MiniPay
• Detecting MiniPay wallet in your dApp
• Creating mobile-first payment applications
• Integrating with MiniPay's discovery page

What is MiniPay?

MiniPay is a stablecoin wallet with a built-in Mini App discovery page. It's available as:

• Built into Opera Mini browser (Android)
• Standalone app (Android and iOS)

Key features:

• Phone number mapping to wallet addresses
• Sub-cent transaction fees
• 2MB lightweight footprint
• Supports USDm, USDC, and USDT — USDT support is mandatory for listing

Quick Start

Create a MiniPay App

npx @celo/celo-composer@latest create -t minipay

This scaffolds a Next.js app pre-configured for MiniPay.

Detecting MiniPay

Check if the user is using MiniPay:

function isMiniPay(): boolean {
  return typeof window !== "undefined" &&
         window.ethereum?.isMiniPay === true;
}

Important: This code must run in a browser environment, not Node.js.

Connecting Wallet

MiniPay automatically injects the wallet. Request account access:

async function connectWallet(): Promise<string | null> {
  if (typeof window === "undefined" || !window.ethereum) {
    return null;
  }

  const accounts = await window.ethereum.request({
    method: "eth_requestAccounts",
    params: [],
  });

  return accounts[0] || null;
}

Important: Hide the "Connect Wallet" button when inside MiniPay - the connection is implicit.

const [address, setAddress] = useState<string | null>(null);
const inMiniPay = isMiniPay();

useEffect(() => {
  if (inMiniPay) {
    connectWallet().then(setAddress);
  }
}, [inMiniPay]);

return (
  <div>
    {!inMiniPay && (
      <button onClick={() => connectWallet().then(setAddress)}>
        Connect Wallet
      </button>
    )}
    {address && <p>Connected: {address}</p>}
  </div>
);

Reading Balances

import { createPublicClient, http, formatUnits } from "viem";
import { celo } from "viem/chains";

const publicClient = createPublicClient({
  chain: celo,
  transport: http(),
});

const USDM_ADDRESS = "0x765de816845861e75a25fca122bb6898b8b1282a";

const ERC20_ABI = [
  {
    name: "balanceOf",
    type: "function",
    stateMutability: "view",
    inputs: [{ name: "account", type: "address" }],
    outputs: [{ type: "uint256" }],
  },
] as const;

async function getUSDmBalance(address: string): Promise<string> {
  const balance = await publicClient.readContract({
    address: USDM_ADDRESS,
    abi: ERC20_ABI,
    functionName: "balanceOf",
    args: [address as `0x${string}`],
  });

  return formatUnits(balance, 18);
}

Sending Transactions

Use viem or wagmi for transactions. MiniPay does not support ethers.js.

import { createWalletClient, custom, parseUnits, encodeFunctionData } from "viem";
import { celo } from "viem/chains";

const USDM_ADDRESS = "0x765de816845861e75a25fca122bb6898b8b1282a";

const ERC20_ABI = [
  {
    name: "transfer",
    type: "function",
    stateMutability: "nonpayable",
    inputs: [
      { name: "to", type: "address" },
      { name: "amount", type: "uint256" },
    ],
    outputs: [{ type: "bool" }],
  },
] as const;

async function sendUSDm(to: string, amount: string): Promise<string> {
  const walletClient = createWalletClient({
    chain: celo,
    transport: custom(window.ethereum),
  });

  const [address] = await walletClient.getAddresses();

  const hash = await walletClient.sendTransaction({
    account: address,
    to: USDM_ADDRESS,
    data: encodeFunctionData({
      abi: ERC20_ABI,
      functionName: "transfer",
      args: [to as `0x${string}`, parseUnits(amount, 18)],
    }),
  });

  return hash;
}

Testing Your Mini App

1. Set Up ngrok

MiniPay cannot access localhost. Use ngrok to create a tunnel:

ngrok http 3000

2. Enable Developer Mode in MiniPay

1. Open MiniPay > Settings > About
2. Tap Version number repeatedly until Developer Mode is enabled
3. Go to Settings > Developer Settings
4. Enable "Use Testnet" for Celo Sepolia

3. Load Your App

1. Open MiniPay > Tap compass icon
2. Select "Test Page"
3. Enter your ngrok HTTPS URL
4. Tap "Go"

Requirements and Limitations

Supported

• Celo Mainnet and Celo Sepolia Testnet only
• viem v2+ and wagmi libraries
• TypeScript v5+, Node.js v20+
• USDm (cUSD), USDC, and USDT stablecoins

Not Supported

• ethers.js (use viem instead)
• EIP-1559 transactions (legacy only)
• Message signing
• Android/iOS emulators (use real device)
• Other blockchain networks

Rules That Block Listing

These are enforced when MiniPay reviews your app. Apply them while writing code — a rule you only discover at submission time has already cost you a rebuild.

• USDT support is mandatory. Every Mini App must transact in USDT natively. Do not add tokens MiniPay does not natively support.

• Never expose the wallet address. No display, no copy-to-clipboard, no share sheet, no address QR — and a truncated 0x123…abc is not an exception; it is still the address. Keep it in state for balanceOf and as the transaction account, but never render it.

  Show a username instead, in this order:

  1. A username the user set — prompt for one at onboarding if your app has any social surface.
  2. A generated display name if they haven't — adjective + noun from a word list, hashed deterministically from the address so it stays stable across sessions without any storage. Users read "clever mango" as a name; they read 0x7a3f… as an error.
  3. "Unknown", or nothing at all.

  Nothing on screen beats a hex string. The phone number via ODIS also works where you genuinely need to identify a real person. A working displayName() helper is in Celopedia → minipay-templates.md §8.

• No withdrawals to arbitrary addresses. No free-text or paste-an-address field. Pay out only to a destination the app controls or that MiniPay resolves.
• Pre-flight against amount + network fee. The fee is paid in the same stablecoin, so balance < amount is a bug — the transfer is affordable, the fee is not, and the transaction reverts in the user's face. Check balance >= amount + fee and redirect to https://link.minipay.xyz/add_cash on a shortfall.
• Three transaction states. Pending from the signature prompt through confirmation; success only on waitForTransactionReceipt, never on submission; failure with descriptive copy. Map errors from codes and error names, not message text — message strings change between provider versions and locales.
• No CELO or crypto jargon in the UI. Say Network fee / Deposit / Withdraw / Stablecoin.
• About, How to Use, Terms, Privacy, and Support must all be reachable from the footer or menu, plus an explicit line stating the app is operated by your organisation and not by Opera or MiniPay.
• Freeze what you submit. See the allowlist entry in references/troubleshooting.md — contract addresses, method signatures, and URLs are enforced after approval.

Full checklist: minipay-requirements.md in the celopedia-skill (celo-org/celopedia-skills).

Dependencies

{
  "dependencies": {
    "viem": "^2.0.0",
    "@celo/abis": "^11.0.0"
  },
  "devDependencies": {
    "typescript": "^5.0.0"
  }
}

Additional Resources

• testing-guide.md - Detailed testing instructions
• troubleshooting.md - Common issues and solutions
• code-examples.md - Gas estimation, fee currency, React hooks

Source of truth: Celopedia

These skills are focused, task-level references. For anything broader — verified contract addresses, ecosystem and protocol data, listing requirements, grants, governance, migration guides, or cross-cutting Celo questions — Celopedia is the canonical source and is kept current. Where this skill and Celopedia disagree, Celopedia wins.

For MiniPay specifically, Celopedia carries what this skill does not: the full two-stage listing checklist (minipay-requirements.md), a symptom → fix router for rejected apps (minipay-common-mistakes.md), the app-fit scorecard, the live Mini App catalog with per-country targeting, the performance playbook for the PageSpeed listing bar, ODIS phone resolution, deeplinks, and MiniPay's custom RPC methods.

npx skills add celo-org/celopedia-skills