## `startPrank`

### Signature

```solidity
function startPrank(address msgSender) external;
function startPrank(address msgSender, bool delegateCall) external;
function startPrank(address msgSender, address txOrigin) external;
function startPrank(address msgSender, address txOrigin, bool delegateCall) external;
```

### Description

Sets `msg.sender` **for all subsequent calls** until [`stopPrank`](/reference/cheatcodes/stop-prank) is called.

Optionally, you can also set `tx.origin` and enable delegate call pranking.

### Parameters

| Parameter      | Type      | Description                                                              |
|----------------|-----------|--------------------------------------------------------------------------|
| `msgSender`    | `address` | The address to set as `msg.sender`                                       |
| `txOrigin`     | `address` | The address to set as `tx.origin` (optional)                             |
| `delegateCall` | `bool`    | If `true`, applies the prank to all subsequent delegate calls (optional) |

### Examples

```solidity [test/StartPrank.t.sol]
function testStartPrank() public {
    vm.startPrank(alice);
    
    // All these calls have msg.sender == alice
    myContract.deposit();
    myContract.transfer(bob, 100);
    myContract.withdraw();
    
    vm.stopPrank();
}
```

#### Pranking Delegate Calls with State Diff Recording

:::code-group
```solidity [test/PrankDelegateCall.t.sol]
function testPrankDelegateCall() public {
    Proxy proxy = new Proxy();
    Implementation impl = new Implementation();
    
    vm.startPrank(address(proxy), true);
    vm.startStateDiffRecording();
    
    (bool success,) = address(impl).delegatecall(
        abi.encodeWithSignature("setNum(uint256)", 42)
    );
    
    VmSafe.AccountAccess[] memory accesses = vm.stopAndReturnStateDiff();
    // accesses[0].accessor == proxy
    // accesses[0].account == impl
    
    vm.stopPrank();
}
```

```solidity [src/Implementation.sol]
contract Implementation {
    uint public num;
    
    function setNum(uint _num) public {
        num = _num;
    }
}
```

```solidity [src/Proxy.sol]
contract Proxy {
    uint public num;
}
```
:::

### Gotchas

:::note
Delegate calls cannot be pranked from an EOA. Use a contract as the prank source when pranking delegate calls.
:::

:::warning
Always call [`stopPrank`](/reference/cheatcodes/stop-prank) when done to avoid affecting subsequent tests.
:::

### Related Cheatcodes

* [`prank`](/reference/cheatcodes/prank) - Sets `msg.sender` for a single call
* [`stopPrank`](/reference/cheatcodes/stop-prank) - Stops an active prank
* [`readCallers`](/reference/cheatcodes/read-callers) - Reads the current caller mode

### See Also

* [`startHoax`](/reference/forge-std/startHoax) - Combines startPrank and deal
* [`changePrank`](/reference/forge-std/change-prank) - Changes the active prank address