# CCIP v1.6.1 Ownable2Step Contract API Reference
Source: https://docs.chain.link/ccip/api-reference/evm/v1.6.1/ownable-2-step
> For the complete documentation index, see [llms.txt](/llms.txt).
## Ownable2Step
A minimal contract that implements 2-step ownership transfer and nothing more. It's made to be minimal to reduce the impact of the bytecode size on any contract that inherits from it.
[Git Source](https://github.com/smartcontractkit/chainlink-evm/blob/contracts-v1.4.0/contracts/src/v0.8/shared/access/Ownable2Step.sol)
> **NOTE**
>
> This contract implements a secure two-step ownership transfer process:
1. Current owner initiates transfer using `transferOwnership`
2. New owner must accept using `acceptOwnership`
3. Transfer only completes after both steps
This prevents accidental transfers to incorrect or inaccessible addresses.
## Events
### OwnershipTransferRequested
```solidity
event OwnershipTransferRequested(address indexed from, address indexed to);
```
**Parameters**
| Name | Type | Description |
| ------ | --------- | ------------------------------------- |
| `from` | `address` | Current owner initiating the transfer |
| `to` | `address` | Proposed new owner |
### OwnershipTransferred
```solidity
event OwnershipTransferred(address indexed from, address indexed to);
```
**Parameters**
| Name | Type | Description |
| ------ | --------- | -------------- |
| `from` | `address` | Previous owner |
| `to` | `address` | New owner |
## Errors
### CannotTransferToSelf
```solidity
error CannotTransferToSelf();
```
### MustBeProposedOwner
```solidity
error MustBeProposedOwner();
```
### OnlyCallableByOwner
```solidity
error OnlyCallableByOwner();
```
### OwnerCannotBeZero
```solidity
error OwnerCannotBeZero();
```
## State Variables
### s\_owner
The owner is the current owner of the contract.
```solidity
address private s_owner;
```
> \*\*NOTE\*\*
>
>
>
> The owner is the second storage variable so any implementing contract could pack other state with it instead of the
> much less used s\_pendingOwner.
### s\_pendingOwner
The pending owner is the address to which ownership may be transferred.
```solidity
address private s_pendingOwner;
```
## Functions
### acceptOwnership
Allows an ownership transfer to be completed by the recipient.
```solidity
function acceptOwnership() external override;
```
> \*\*NOTE\*\*
>
>
>
> Reverts with `MustBeProposedOwner` if caller is not the pending owner.
>
> When successful:
>
> - Updates owner to the caller
> - Clears pending owner
> - Emits OwnershipTransferred event
### constructor
Initializes the contract with an owner and optionally a pending owner.
```solidity
constructor(address newOwner, address pendingOwner);
```
> \*\*NOTE\*\*
>
>
>
> - Reverts with `OwnerCannotBeZero` if newOwner is address(0)
> - Sets newOwner as the initial owner
> - If pendingOwner is not address(0), initiates ownership transfer to pendingOwner
**Parameters**
| Name | Type | Description |
| -------------- | --------- | -------------------------------------------------- |
| `newOwner` | `address` | The initial owner of the contract |
| `pendingOwner` | `address` | Optional address to initiate ownership transfer to |
### onlyOwner
Modifier that restricts function access to the contract owner.
```solidity
modifier onlyOwner();
```
### owner
Returns the current owner's address.
```solidity
function owner() public view override returns (address);
```
**Returns**
| Type | Description |
| --------- | -------------------------------- |
| `address` | The address of the current owner |
### transferOwnership
Allows an owner to begin transferring ownership to a new address.
```solidity
function transferOwnership(address to) public override onlyOwner;
```
> \*\*NOTE\*\*
>
>
>
> The new owner must call `acceptOwnership` to complete the transfer. No permissions are changed until acceptance.
>
> Reverts with:
>
> - `OnlyCallableByOwner` if caller is not the current owner
> - `CannotTransferToSelf` if attempting to transfer to current owner
**Parameters**
| Name | Type | Description |
| ---- | --------- | -------------------------------------------------- |
| `to` | `address` | The address to which ownership will be transferred |
### \_validateOwnership
Internal function to validate access control.
```solidity
function _validateOwnership() internal view;
```