Alchemy Install & Auth

Overview

Install the alchemy-sdk npm package and configure API authentication. Alchemy provides blockchain infrastructure (RPC nodes, Enhanced APIs, NFT APIs, webhooks) across Ethereum, Polygon, Arbitrum, Optimism, Base, and Solana.

Prerequisites

Node.js 18+ (or Python 3.10+ for alchemy-sdk Python)
Free Alchemy account at alchemy.com
API key from Alchemy Dashboard

Instructions

Step 1: Install the Alchemy SDK

# JavaScript/TypeScript (official SDK)
npm install alchemy-sdk

# Python (community SDK)
pip install alchemy-sdk

Step 2: Create an Alchemy App

Go to dashboard.alchemy.com
Click "Create new app"
Select chain: Ethereum, Polygon, Arbitrum, Optimism, Base, or Solana
Select network: Mainnet, Sepolia (testnet), or Mumbai
Copy the API key

Step 3: Configure Environment

# Set environment variable
export ALCHEMY_API_KEY="your-api-key-here"

# Or create .env file
cat > .env << 'EOF'
ALCHEMY_API_KEY=your-api-key-here
ALCHEMY_NETWORK=ETH_MAINNET
EOF

echo ".env" >> .gitignore

Step 4: Initialize and Verify

// src/alchemy-client.ts
import { Alchemy, Network } from 'alchemy-sdk';

const alchemy = new Alchemy({
  apiKey: process.env.ALCHEMY_API_KEY,
  network: Network.ETH_MAINNET,
});

// Verify connection
async function verifyConnection() {
  const blockNumber = await alchemy.core.getBlockNumber();
  console.log(`Connected! Latest block: ${blockNumber}`);
  return blockNumber;
}

verifyConnection().catch(console.error);

Step 5: Multi-Chain Configuration

// src/config/chains.ts
import { Alchemy, Network } from 'alchemy-sdk';

// Create clients for multiple chains
const chains = {
  ethereum: new Alchemy({ apiKey: process.env.ALCHEMY_API_KEY, network: Network.ETH_MAINNET }),
  polygon: new Alchemy({ apiKey: process.env.ALCHEMY_API_KEY, network: Network.MATIC_MAINNET }),
  arbitrum: new Alchemy({ apiKey: process.env.ALCHEMY_API_KEY, network: Network.ARB_MAINNET }),
  optimism: new Alchemy({ apiKey: process.env.ALCHEMY_API_KEY, network: Network.OPT_MAINNET }),
  base: new Alchemy({ apiKey: process.env.ALCHEMY_API_KEY, network: Network.BASE_MAINNET }),
};

export default chains;

Supported Networks

Chain	Network Enum	Mainnet	Testnet
Ethereum	`ETH_MAINNET`	Yes	Sepolia
Polygon	`MATIC_MAINNET`	Yes	Amoy
Arbitrum	`ARB_MAINNET`	Yes	Sepolia
Optimism	`OPT_MAINNET`	Yes	Sepolia
Base	`BASE_MAINNET`	Yes	Sepolia
Solana	`SOL_MAINNET`	Yes	Devnet

Output

alchemy-sdk installed in node_modules
API key configured in environment
Verified connection with latest block number
Multi-chain client configuration ready

Examples

Create a development-only Alchemy application for Sepolia or another supported test network, store its key in a local ignored environment file or platform secret store, and run verifyConnection. A successful setup prints a current block number from the selected test network without printing the key. Add a second client only when the application genuinely needs another chain, and keep the network selection explicit per client. If verification returns 401, the network is unsupported, or the variable is absent, correct the dashboard or environment configuration before proceeding; do not reuse a production key in local examples or commit it to the repository.

Error Handling

Error	Cause	Solution
`Must provide apiKey`	Missing env var	Set `ALCHEMY_API_KEY` in environment
`401 Unauthorized`	Invalid API key	Verify key in Alchemy Dashboard
`429 Rate Limit`	Free tier exceeded	Upgrade plan or reduce request rate
`ECONNREFUSED`	Network blocked	Ensure HTTPS to *.g.alchemy.com allowed

Resources

Next Steps

Proceed to alchemy-hello-world for your first blockchain query.