Hardhat not able to fork the mainnet

Question

I want to fork the polygon mainnet using hardhat but don't know why it's giving me this error:

Error HH604: Error running JSON-RPC server: Invalid JSON-RPC response's result.

Errors: Invalid value null supplied to : RpcBlockWithTransactions | null/transactions: RpcTransaction Array/0: RpcTransaction/accessList: Array<{ address: DATA, storageKeys: Array<DATA> | null }> | undefined, Invalid value null supplied to : RpcBlockWithTransactions | null/transactions: RpcTransaction Array/2: RpcTransaction/accessList: Array<{ address: DATA, storageKeys: Array<DATA> | null }> | undefined

or sometimes it gives me this error:

Error HH110: Invalid JSON-RPC response received: {
  "message":"No API key found in request"
}

I am also providing the API with rpc URL but still I am getting this error. I am able to make a curl request but don't know why this is happening. Is it a problem from my side or from the node provider?

This is the command I am running in the terminal for forking: yarn hardhat node --fork https://polygon-mainnet.g.alchemy.com/v2/<api-key>

Answer 1

The error is clearly displayed in your code - without your API key you’re not providing any method for connecting to the blockchain.

Go to, say, Alchemy here, create a free account and set up a new tool - fork_polygon_mainnet or whatever. Then choose that tool, click ‘view key’, and paste the API key provided there into your yarn command where it says <api-key>

If you still have issues, look at Alchemy’s docs. They have copy/paste utilities for forking networks, as well as a plethora of web3 & ethers.js type commands in their SDK - check out the composer on Alchemy.