Mainnet Wallet Setup

Before working with gasless transactions on Polygon mainnet, you need a wallet with real funds. This lesson generates a new wallet and shows you how to secure it properly.

Why Mainnet?

Unlike Section 5, which used the Amoy testnet, this section requires Polygon mainnet. OpenGSN relay networks operate on mainnet where real economic incentives keep relays running. The patterns you learn here translate directly to production apps.

Generate Your Wallet

Run the script to create a random wallet. You will receive three pieces of information:

1. Address: Your public identifier on Polygon.
2. Private Key: A 64-character hex string that controls your funds.
3. 24-Word Mnemonic: A human-readable backup phrase.

import { ethers } from 'ethers'

const wallet = ethers.Wallet.createRandom()

console.log('Address:', wallet.address)
console.log('Private Key:', wallet.privateKey)
console.log('Mnemonic:', wallet.mnemonic.phrase)

Security First

⚠️ CRITICAL: Anyone with your private key or mnemonic can spend your funds.

Do:

• Store both in a password manager.
• Write the mnemonic on paper and keep it safe.
• Never share them with anyone.

Don’t:

• Screenshot or email your credentials.
• Store them in plain text on your computer.
• Reuse this wallet for large amounts in production.

This is a learning wallet. Keep only enough funds to complete the tutorial (~5 USDT and 0.1 POL).

Import into Nimiq Wallet (Optional)

For a better UX, import your 24-word mnemonic into the Nimiq Wallet:

1. Visit https://wallet.nimiq.com
2. Select “Import with Recovery Words”
3. Paste your 24-word phrase
4. Access your wallet through a friendly interface

The Nimiq Wallet supports Polygon and makes managing tokens easier than the command line.

Get Mainnet Funds

USDT (for core gasless transfers)

You will use USDT for the baseline and OpenGSN lessons (Lessons 3–6). There is no public faucet for USDT on Polygon mainnet, so you must:

• Purchase USDT on an exchange and withdraw to Polygon
• Swap into USDT on Polygon using a DEX such as Uniswap
• Bridge USDT from Ethereum mainnet

Aim for 2–5 USDT to comfortably complete the exercises.

USDC (for the permit lesson)

USDC is only needed for the EIP-2612 permit lesson (Lesson 7). For Polygon mainnet USDC you must use a real liquidity source. Typical options are:

• Purchase USDC on an exchange and withdraw directly to Polygon
• Bridge USDC from another chain (for example Ethereum mainnet) using a trusted bridge
• Swap into USDC on Polygon via a DEX such as Uniswap

If you want to practice on testnets before touching mainnet, you can use https://faucet.circle.com/ to obtain testnet USDC on supported networks. That testnet USDC is not usable on Polygon mainnet.

POL (for gas in gasful baseline lesson)

For Polygon mainnet POL you cannot use the Polygon faucet (it only serves testnets like Amoy). Instead:

• Acquire POL on an exchange and withdraw to Polygon mainnet, or
• Bridge POL (or wrapped MATIC) from another network.

You only need ~0.1 POL for the baseline gasful transaction in the next lesson, but it must be real mainnet POL.

Save Your Private Key

Copy your private key from the terminal output. In the following lessons, load it from an environment variable instead of hardcoding it in source code. For example:

SENDER_PRIVATE_KEY=0xYOUR_PRIVATE_KEY_FROM_LESSON_1

import dotenv from 'dotenv'

dotenv.config()

const wallet = new ethers.Wallet(process.env.SENDER_PRIVATE_KEY, provider)

Never commit .env files with real private keys to version control.

Verify Your Setup

Before moving forward, confirm:

• ✅ Private key and mnemonic are stored securely
• ✅ Wallet address is funded with USDC and POL
• ✅ You understand the security risks

Next Up

In Introduction to Gasless Transactions, you will learn why gasless transactions matter and see the architecture that makes them possible.