How to Get Contract Deployment Transactions in a Block (2024)

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API Endpoint

This tutorial uses the getBlockWithTransactions and getBlock endpoints.

A transaction that represents the creation of a new smart contract is called a contract deployment transaction. These transactions provide valuable information about the creation of new contracts, such as the address of the contract, the code, and the parameterss passed to the contract's constructor. Apps like Opensea use contract deployment transactions to monitor the deployment of new NFT contracts on the network.

In this tutorial, we will be using the Alchemy SDK to retrieve contract deployment transactions in a specific block on the Ethereum blockchain. The same applies to any EVM blockchain. So, let's get started by setting up the developer environment!

In case you haven't already, install node and npm on your local machine.

Make sure that node is at least v14 or higher by typing the following in your terminal:

node -v

Step 2: Create an Alchemy App

See Also

Deploying a smart contract using Hardhat | BaseCost & How to create smart contract on Ethereum, Binance & Polygon

In case you haven't already, sign up for a free Alchemy account.

Next, navigate to the Alchemy Dashboard and create a new app. Make sure you set the chain to Ethereum and the network to Mainnet. Once the app is created, click on your app's View Key button on the dashboard. Take note of the API KEY.

You will need this later.

Let's now create an empty repository and install all the node dependencies.

mkdir get-contractDeployments && get-contractDeploymentsnpm init -ynpm install alchemy-sdktouch main.js

This will create a repository named get-contractDeployments that holds all your files and dependencies. Next, open this repo in your favorite code editor. We will write our code in the main.js file.

We will look at two ways in which we can find the contract deployment transactions in a block:

• The first approach uses the fact that there is no to address for a contract deployment transaction. This is true because when a contract is deployed, it does not have an address yet, as it does not exist on the blockchain. Therefore, the to field in the transaction is set to null.
• The second approach identifies a contract deployment transaction by looking at the type of OPCODE for the transaction. If the type is CREATE or CREATE2 then it is a contract deployment transaction, otherwise not.

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CREATE and CREATE2

CREATE and CREATE2 are OPCODES that are observed during a contract deployment.

CREATE is the original way of creating a new smart contract. It deploys a smart contract by creating a new contract address. The contract address is determined by the contract creator's address and the nonce of the creator's account.

CREATE2, on the other hand, is a more recent addition to the Ethereum protocol, introduced in the Constantinople hard fork. It allows for the creation of contracts at a specified address, determined by the combination of a salt value and the contract code's keccak256 hash. This allows for more flexibility when creating smart contracts. For more information read Alchemy's guide on deriving contract addresses using CREATE2.

Both CREATE and CREATE2 transactions have the to field set to null because the contract address is not known at the time of deployment.

Writing the script

Add the following code to the main.js file. Here's an overview of what the code is doing (also explained in the comments):

1. The code imports the necessary modules from the Alchemy SDK.
2. Configures the API Key and network to interact with the Ethereum blockchain.
3. Creates a new instance of the Alchemy class using the previously defined settings to interact with the SDK.
4. Declares a variable blockHashOrNumber and assigns it a block number or hash.
5. Uses the getBlockWithTransactions method to retrieve information about the block and its transactions.
6. Retrieves the transactions in the block.
7. Creates an array contractDeploymentTxHashes to store the transaction hashes of contract deployment transactions.
8. Loops through the transactions in the block, checking if each transaction is a contract deployment by checking if the to address is null.
9. If the transaction is a contract deployment, add its tx hash to the array of contract deployment transaction hashes.
10. Logs the array of contract deployment transaction hashes.

// Importing the Alchemy SDKconst { Network, Alchemy } = require("alchemy-sdk");// Configuring the Alchemy SDKconst settings = { apiKey: "demo", // Replace with your Alchemy API Key. network: Network.ETH_MAINNET, // Replace with your network.};// Creating a new Alchemy instance to interact with the Alchemy APIsconst alchemy = new Alchemy(settings);async function main() { // Block number or hash to get contract deployment transactions from let blockHashOrNumber = 15530600; // Using the getBlock method to get information about the block and its transactions let block = await alchemy.core.getBlockWithTransactions(blockHashOrNumber); // Getting the transactions in the block let blockTxs = block.transactions; // Creating an array to store the tx hashes of contract deployment transactions let contractDeploymentTxHashes = []; // Looping through the transactions of block and for each transaction checking if it is a contract deployment transaction for (const tx of blockTxs) { // Checking if the transaction is a contract deployment (because the `to` address is `null` for contract deployments) let isContractDeployment = tx.to === null; // If the transaction is a contract deployment, add its tx hash to the array of contract deployment transaction hashes if (isContractDeployment) { contractDeploymentTxHashes.push(tx.hash); } } // Logging the array of contract deployment transaction hashes console.log(contractDeploymentTxHashes);}// Calling the main function to run the codemain();

Testing the Script

Run the script using the following command:

node main.js

You should see an array containing the transaction hashes of contract deployment transactions in the block as the output.

[ '0x38a071a0282808c67a8a046f34f5e3dc1145789b6af1118e3b060f9293cb0408']

In this case, we only had 1 contract deployment transaction in the given block. You can check out this transaction on Etherscan.

Approach 2: OPCODES

Writing the script

Add the following code to the main.js file. Here's an overview of what the code is doing (also explained in the comments):

1. The code imports the necessary modules from the Alchemy SDK.
2. Configures the API Key and network to interact with the Ethereum blockchain.
3. Creates a new instance of the Alchemy class using the previously defined settings to interact with the SDK.
4. Declares a variable blockHashOrNumber and assigns it a block number or hash.
5. Uses the getBlock method to retrieve information about the block.
6. Extracts the transaction hashes of all the transactions in the block.
7. Creates an array contractDeploymentTxHashes to store the transaction hashes of contract deployment transactions.
8. Loops through the transaction hashes in the block.
9. For each transaction hash it uses the traceTransaction method of debug namespace to get the traces for that transaction.
10. Checking if the transaction is a contract deployment by checking the type of transaction, if it is "CREATE" or "CREATE2".
11. If the transaction is a contract deployment, add its tx hash to the array of contract deployment transaction hashes.
12. Logs the array of contract deployment transaction hashes.

// Importing the Alchemy SDKconst { Network, Alchemy } = require("alchemy-sdk");// Configuring the Alchemy SDKconst settings = { apiKey: "demo", // Replace with your Alchemy API Key. network: Network.ETH_MAINNET, // Replace with your network.};// Creating a new Alchemy instance to interact with the Alchemy APIsconst alchemy = new Alchemy(settings);async function main() { // Block number or hash to get contract deployment transactions from let blockHashOrNumber = 15530600; // Using the getBlock method to get information about the block let block = await alchemy.core.getBlock(blockHashOrNumber); // Extracting the transaction hashes of all the transactions in the block let blockTxHashes = block.transactions; // Creating an array to store the tx hashes of contract deployment transactions let contractDeploymentTxHashes = []; console.log("getting the contract deployment transactions..."); // Looping through the transactions of block and for each transaction checking if it is a contract deployment transaction for (const txHash of blockTxHashes) { // Using the debug_traceTransaction method to get the trace of the transaction let txTrace = await alchemy.debug.traceTransaction(txHash, { // using callTracer as tracer type to get the traces for the transaction type: "callTracer", }); // Checking if the transaction is a contract deployment (because CREATE and CREATE2 OPCODES are used for contract deployments) let isContractDeployment = txTrace.type === "CREATE" || txTrace.type === "CREATE2"; // If the transaction is a contract deployment, add its tx hash to the array of contract deployment transaction hashes if (isContractDeployment) { contractDeploymentTxHashes.push(txHash); } } // Logging the array of contract deployment transaction hashes console.log(contractDeploymentTxHashes);}// Calling the main function to run the codemain();

Testing the Script

Run the script using the following command:

node main.js

You should see an array containing the transaction hashes of contract deployment transactions in the block as the output.

getting the contract deployment transactions...[ '0x38a071a0282808c67a8a046f34f5e3dc1145789b6af1118e3b060f9293cb0408']

1. Number of API Calls: In terms of API calls, Approach 1 (checking if the to address is null) is better than Approach 2 (checking for CREATE and CREATE2 OPCODES) because in the first method, we are only making one API call to the getBlockWithTransactions endpoint but in the second approach, we first get the transaction hashes for all the transactions in the block using the getBlock method and then for each transaction hash we call the traceTransaction method to get the traces for that transaction. So, if there are n transactions in the block, we are making n + 1 API calls in the second approach but only 1 using the first approach.

2. Speed: It takes time to make an API call as the request is sent to the server and the response is returned over the network. Due to more API calls, the second approach becomes slower than the first.

Therefore, generally, you would prefer the first approach but there might be cases when you are already making those API calls for doing some other stuff in your code, in those cases, you can use the second approach as well.

Congratulations! You now know how to get contract deployment transactions in a block 🎉

Happy Coding and feel free to message us with any related questions on Alchemy's Discord Server!