# createSelectFork

Description: createSelectFork cheatcode documentation

Note: This document was authored using MDX

  Source: https://github.com/NomicFoundation/hardhat-website/tree/main/src/content/docs/docs/reference/cheatcodes/Forking/create-select-fork.mdx

{/* This document contains content copied/adapted from the Foundry Book (MIT licensed). See LICENSE in the parent directory. */}

### Signature

```solidity
function createSelectFork(
  string calldata urlOrAlias
) external returns (uint256);
```

```solidity
function createSelectFork(
  string calldata urlOrAlias,
  uint256 block
) external returns (uint256);
```

```solidity
function createSelectFork(
  string calldata urlOrAlias,
  bytes32 transaction
) external returns (uint256);
```

### Description

Creates _and_ selects a new fork from the given endpoint and returns the identifier of the fork. If a block number is passed as an argument, the fork will begin on that block, otherwise it will begin on the _latest_ block.

If a transaction hash is provided, it will roll the fork to the block the transaction was mined in and replays all previously executed transactions.

### Examples

Create and select a new mainnet fork with the latest block number:

```solidity
uint256 forkId = vm.createSelectFork(MAINNET_RPC_URL);

assertEq(block.number, 15_171_037); // as of time of writing, 2022-07-19 04:55:27 UTC
```

Create and select a new mainnet fork with a given block number:

```solidity
uint256 forkId = vm.createSelectFork(MAINNET_RPC_URL, 1_337_000);

assertEq(block.number, 1_337_000);
```

### SEE ALSO

- [createFork](/docs/reference/cheatcodes/forking/create-fork)
- [selectFork](/docs/reference/cheatcodes/forking/select-fork)