Ownable2Step API Reference

Ownable2Step is a reusable ownership primitive that manages contract ownership through a two-step transfer process: propose → accept.

If you implement this contract, ownership is transferred by proposing a new owner and requiring that owner to explicitly accept the role.

Usage Boundary

You do not call this contract directly in most cases.

Contracts inherit this implementation to manage ownership.
Administrators call these functions to transfer ownership.
You are responsible for completing the full transfer lifecycle (proposal and acceptance).

@chainlink/contracts/src/v0.8/shared/access/Ownable2Step.sol

import {Ownable2Step} from "@chainlink/contracts/src/v0.8/shared/access/Ownable2Step.sol";

abstract contract Ownable2Step is IOwnable

address private s_owner;
address private s_pendingOwner;

constructor(address newOwner, address pendingOwner)

Initializes ownership and optional pending owner.

Reverts if newOwner is the zero address.

If a pending owner is provided at deployment, ownership can be accepted immediately by that address.

function owner()
  public
  view
  override
  returns (address)

Returns the current owner of the contract.

function transferOwnership(address to)
  public
  override

Proposes a new owner.

Only callable by the current owner.
Sets the pending owner and replaces any existing pending ownership proposal (previous pending owners can no longer accept ownership).
Reverts if the proposed owner is the zero address.

function acceptOwnership()
  external
  override

Accepts ownership of the contract.

function _transferOwnership(address to)
  internal

Sets the pending owner.

function _validateOwnership()
  internal
  view

event OwnershipTransferRequested(address indexed from, address indexed to);
event OwnershipTransferred(address indexed from, address indexed to);

For a cross-contract event index, see Events.

error OwnerCannotBeZero();
error MustBeProposedOwner();
error CannotTransferToSelf();
error OnlyCallableByOwner();

For a cross-contract error index, see Errors

Ownership transfer follows a two-step process: propose → accept.
Ownership transfer is not complete until the pending owner calls acceptOwnership.
Ownership transfer is pull-based: the proposed owner must actively accept ownership.
While a pending owner is set, the current owner retains full control.
A new ownership proposal overwrites any existing pending owner.
If the pending owner does not call acceptOwnership, ownership remains with the current owner indefinitely.

Ownership cannot be transferred without explicit acceptance by the proposed owner.
Only the current owner can initiate ownership transfers.
Prevents accidental or unauthorized ownership changes.