Hardhat gives a same address for every deployment on the localhost

Question

I am trying to develop my project using React, Ethers, and Hardhat. Whenever I run the below commands in order, the hardhat gives me the same address as previously deployed contracts. So weird! I might be wrong somewhere.

1. First I start the node by: "npx hardhat node"
2. Then in another terminal I run: "npx hardhat compile"
3. Then this command on the same terminal as the last: "npx hardhat run scripts/deploy-script.js --network localhost"

This process always gives me the same address, although I may have made some changes to the scripts. It is expected to give a new address for every newly deployed contract, all of the addresses are the same.

Does anybody know where I am wrong?

The contract address is always the same as past

Answer 1

When you start a Hardhat node, it uses a hardcoded list of private keys to generate accounts for you (it lists these when you start the node). And because these are fresh accounts (in the context of the blockchain, since it's a new blockchain) their nonce starts at zero.

Since contract addresses (with regular deployment, not with CREATE2) are calculated based on the sender's address (which is always the same, since Hardhat uses hardcoded private key) and the account nonce, the contract address is also always the same. You can read here more about contract address generation: https://ethereum.stackexchange.com/a/761/31933