> For the complete documentation index, see [llms.txt](https://docs.phase.cash/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.phase.cash/proxies/storage-upgradeable-proxy.md).

# Storage Upgradeable Proxy

The Storage Upgradeable Proxy is based on reading the target from a slot from a Storage. This means multiple proxies can read from the same slot and can all be upgraded at once by changing that Storage slot.

{% hint style="info" %}
The Storage mentioned here is not the internal storage of the contract but a separate contract capable of storing and reading storage slots. This means data is stored elsewhere than the proxy contract itself and can be updated independently of it.
{% endhint %}

{% code title="StorageUpgradeableProxy.sol" overflow="wrap" lineNumbers="true" %}

```solidity
contract StorageUpgradeableProxy is ProxyOwnable, Proxy {
  bytes32 internal constant _STORAGE_SLOT =
    bytes32(uint256(keccak256("proxy.storage")) - 1);

  bytes32 internal constant _SLOT_SLOT =
    bytes32(uint256(keccak256("proxy.storage.slot")) - 1);

  event Upgraded(address indexed _newStorage, bytes32 indexed _newSlot);

  constructor(
    address _owner,
    address _storage,
    bytes32 _slot,
    bytes memory _initialCall
  );

  function upgradeTo(
    address _newStorage,
    bytes32 _newSlot,
    bytes memory _oldImplementationData,
    bytes memory _newImplementationData
  ) external;

  function implementation()
    public
    view
    override
    returns (address _implementation);

  function proxyType() public pure override returns (uint256 _type);

  function _setImplementation(address _newStorage, bytes32 _newSlot) internal;
}
```

{% endcode %}