## Cloning verified contracts

`forge clone` downloads verified Solidity source and compiler settings from a block explorer, initializes a Forge project, compiles it, and writes deployment metadata to `.clone.meta`.

By default, Forge clones the exact address you provide. Add `--implementation` when the address is a proxy and you want the implementation reported by Etherscan.

### Prerequisites

* An explorer-verified contract.
* An Etherscan API key, supplied through `ETHERSCAN_API_KEY` or `--etherscan-api-key`.
* The contract's chain name or chain ID when it is not on Ethereum mainnet.

### Clone the contract at an address

Pass the contract address and the directory that Forge should create:

```bash
$ forge clone \
  --chain mainnet \
  0xC02aB1A5eaA8d1B114EF786D9bde108cD4364359 \
  sparklend-usds
```

This clones the verified contract at the supplied address. If the address is a proxy, the generated project contains the proxy source unless you request its implementation explicitly.

### Clone a proxy implementation

Add `--implementation` to clone the implementation address reported in the proxy's Etherscan metadata:

```bash
$ forge clone \
  --implementation \
  --chain mainnet \
  0xC02aB1A5eaA8d1B114EF786D9bde108cD4364359 \
  sparklend-usds
```

Forge uses the resolved implementation for:

* Downloaded source code and compiler settings.
* Contract creation data and constructor arguments.
* The compiled storage layout.
* The address, contract name, and source path recorded in `.clone.meta`.

If Etherscan does not mark the supplied address as a proxy, `--implementation` clones the supplied address normally.

### Understand implementation resolution

Implementation resolution follows one Etherscan metadata link. Forge fetches the implementation reported for the supplied proxy and stops there, even if that implementation is also marked as a proxy. This avoids following an unrelated delegate-call target reported by the explorer.

The resolved target must be a Solidity contract. A Vyper proxy can still resolve to a Solidity implementation because Forge only compiles the selected target.

When verified sources remain under `lib`, Forge creates an import-only entry point such as `src/Clone.sol` so the compiler discovers the cloned target. The downloaded library sources remain under `lib`.

`--implementation` is supported only with Etherscan. It cannot be combined with `--source sourcify` or `--sourcify-url`, and resolution depends on the proxy metadata returned by the explorer.

### Next steps

* See the [`forge clone` reference](/reference/forge/clone) for all command options.
* Compare storage layouts when [upgrading contracts](/guides/upgrading-contracts).