Using with Foundry

Foundry library for deploying and managing upgradeable contracts, which includes upgrade safety validations.


Follow one of the sections below depending on which version of OpenZeppelin Contracts you are using. OpenZeppelin Contracts v5 is required for new deployments.

Using OpenZeppelin Contracts v5

Run these commands:

forge install foundry-rs/forge-std
forge install OpenZeppelin/openzeppelin-foundry-upgrades
forge install OpenZeppelin/openzeppelin-contracts-upgradeable

Set the following in remappings.txt, replacing any previous definitions of these remappings:

The above remappings mean that both @openzeppelin/contracts/ (including proxy contracts deployed by this library) and @openzeppelin/contracts-upgradeable/ come from your installation of the openzeppelin-contracts-upgradeable submodule and its subdirectories, which includes its own transitive copy of openzeppelin-contracts of the same release version number. This format is needed for Etherscan verification to work. Particularly, any copies of openzeppelin-contracts that you install separately are NOT used.

Using OpenZeppelin Contracts v4

Run these commands, replacing v4.9.6 with the specific version of OpenZeppelin Contracts that you are using:

forge install foundry-rs/forge-std
forge install OpenZeppelin/openzeppelin-foundry-upgrades
forge install OpenZeppelin/[email protected]
forge install OpenZeppelin/[email protected]

Set the following in remappings.txt:

Use LegacyUpgrades.sol instead of Upgrades.sol to upgrade existing deployments that were created with OpenZeppelin Contracts v4.

Foundry Requirements

This library requires forge-std version 1.8.0 or higher.

Before Running

This library uses the OpenZeppelin Upgrades CLI for upgrade safety validations, which are run by default during deployments and upgrades.

If you want to be able to run upgrade safety validations, the following are needed:

  1. Install Node.js.

  2. Configure your foundry.toml to enable ffi, ast, build info and storage layout:

ffi = true
ast = true
build_info = true
extra_output = ["storageLayout"]
  1. If you are upgrading your contract from a previous version, add the @custom:oz-upgrades-from <reference> annotation to the new version of your contract according to Define Reference Contracts or specify the referenceContract option when calling the library’s functions.

  2. Run forge clean before running your Foundry script or tests, or include the --force option when running forge script or forge test.

If you do not want to run upgrade safety validations, you can skip the above steps and use the unsafeSkipAllChecks option when calling the Upgrades library’s functions, or use the UnsafeUpgrades library instead. Note that these are dangerous options meant to be used as a last resort.

Optional: Custom output directory

By default, this library assumes your Foundry output directory is set to "out".

If you want to use a custom output directory, set it in your foundry.toml and provide read permissions for the directory. For example (replace my-output-dir with the directory that you want to use):

out = "my-output-dir"
fs_permissions = [{ access = "read", path = "my-output-dir" }]

Then in a .env at your project root, set the FOUNDRY_OUT environment variable to match the custom output directory, for example:


Windows environments

If you are using Windows, set the OPENZEPPELIN_BASH_PATH environment variable to the fully qualified path of the bash executable. For example, if you are using Git for Windows, add the following line in the .env file of your project (using forward slashes):

OPENZEPPELIN_BASH_PATH="C:/Program Files/Git/bin/bash"


Depending on which major version of OpenZeppelin Contracts you are using, and whether you want to run upgrade safety validations and/or use OpenZeppelin Defender, use the table below to determine which library to import:

OpenZeppelin Contracts v5 OpenZeppelin Contracts v4

Runs validations, supports Defender

import {Upgrades} from "openzeppelin-foundry-upgrades/Upgrades.sol";

import {Upgrades} from "openzeppelin-foundry-upgrades/LegacyUpgrades.sol";

No validations, does not support Defender

import {UnsafeUpgrades} from "openzeppelin-foundry-upgrades/Upgrades.sol";

import {UnsafeUpgrades} from "openzeppelin-foundry-upgrades/LegacyUpgrades.sol";

Import one of the above libraries in your Foundry scripts or tests, for example:

import {Upgrades} from "openzeppelin-foundry-upgrades/Upgrades.sol";

Also import the implementation contract that you want to validate, deploy, or upgrade to, for example:

import {MyToken} from "src/MyToken.sol";

Then call functions from the imported library to run validations, deployments, or upgrades.


The following examples assume you are using OpenZeppelin Contracts v5 and want to run upgrade safety validations.

Deploy a UUPS proxy:

address proxy = Upgrades.deployUUPSProxy(
    abi.encodeCall(MyContract.initialize, ("arguments for the initialize function"))

Deploy a transparent proxy:

address proxy = Upgrades.deployTransparentProxy(
    abi.encodeCall(MyContract.initialize, ("arguments for the initialize function"))

Call your contract’s functions as normal, but remember to always use the proxy address:

MyContract instance = MyContract(proxy);

Upgrade a transparent or UUPS proxy and call an arbitrary function (such as a reinitializer) during the upgrade process:

    abi.encodeCall(, ("arguments for foo"))

Upgrade a transparent or UUPS proxy without calling any additional function:

When upgrading a proxy or beacon, ensure that the new contract either has its @custom:oz-upgrades-from <reference> annotation set to the current implementation contract used by the proxy or beacon, or set it with the referenceContract option, for example:
Options memory opts;
opts.referenceContract = "MyContractV1.sol";
Upgrades.upgradeProxy(proxy, "MyContractV2.sol", "", opts);
// or Upgrades.upgradeBeacon(beacon, "MyContractV2.sol", opts);

Deploy an upgradeable beacon:

address beacon = Upgrades.deployBeacon("MyContract.sol", INITIAL_OWNER_ADDRESS_FOR_BEACON);

Deploy a beacon proxy:

address proxy = Upgrades.deployBeaconProxy(
    abi.encodeCall(MyContract.initialize, ("arguments for the initialize function"))

Upgrade a beacon:

Upgrades.upgradeBeacon(beacon, "MyContractV2.sol");

Coverage Testing

To enable code coverage reports with forge coverage, use the following deployment pattern in your tests: instantiate your implementation contracts directly and use the UnsafeUpgrades library. For example:

address implementation = address(new MyContract());
address proxy = Upgrades.deployUUPSProxy(
    abi.encodeCall(MyContract.initialize, ("arguments for the initialize function"))
UnsafeUpgrades is not recommended for use in Forge scripts. It does not validate whether your contracts are upgrade safe or whether new implementations are compatible with previous ones. Ensure you run validations before any actual deployments or upgrades, such as by using the Upgrades library in scripts.

Deploying and Verifying

Run your script with forge script to broadcast and deploy. See Foundry’s Solidity Scripting guide.

Include the --sender <ADDRESS> flag for the forge script command when performing upgrades, specifying an address that owns the proxy or proxy admin. Otherwise, OwnableUnauthorizedAccount errors will occur.
Include the --verify flag for the forge script command if you want to verify source code such as on Etherscan. This will verify your implementation contracts along with any proxy contracts as part of the deployment.


See Foundry Upgrades API for the full API documentation.