> ## Documentation Index
> Fetch the complete documentation index at: https://docs.crossmint.com/llms.txt
> Use this file to discover all available pages before exploring further.

# External Wallet Signer

> Configure an external wallet or keypair as a signer at wallet creation.

<Note>
  **This page has been updated for Wallets SDK V1.** If you are using the previous version,
  see the [previous version of this page](/wallets/v0/guides/signers/external-wallet) or the [V1 migration guide](/wallets/guides/migrate-to-v1).
</Note>

Use an external wallet signer to connect an existing blockchain wallet or raw keypair — such as MetaMask, Phantom, or a backend keypair — as an operational signer on a Crossmint smart wallet. This is the right choice when your users already have a wallet they want to use to control a Crossmint smart wallet.

Supported on **EVM, Solana, and Stellar**.

## Configuration

Configure the wallet with an external wallet as the operational signer at creation time. The `address` is the public address of the external wallet.

<Tabs>
  <Tab title="React">
    Using `createOnLogin` on the provider:

    ```tsx theme={null}
    import {
        CrossmintProvider,
        CrossmintAuthProvider,
        CrossmintWalletProvider,
    } from "@crossmint/client-sdk-react-ui";

    function App({ children }) {
        return (
            <CrossmintProvider apiKey="YOUR_CLIENT_API_KEY">
                <CrossmintAuthProvider loginMethods={["email"]}>
                    <CrossmintWalletProvider
                        createOnLogin={{
                            chain: "base-sepolia",
                            recovery: { type: "email" },
                            signers: [{
                                type: "external-wallet",
                                address: "0x1234...abcd",
                            }],
                        }}
                    >
                        {children}
                    </CrossmintWalletProvider>
                </CrossmintAuthProvider>
            </CrossmintProvider>
        );
    }
    ```

    Or create the wallet explicitly:

    ```typescript theme={null}
    import { useWallet } from "@crossmint/client-sdk-react-ui";

    const { createWallet } = useWallet();

    const wallet = await createWallet({
        chain: "base-sepolia",
        recovery: { type: "email", email: "user@example.com" },
        signers: [{
            type: "external-wallet",
            address: "0x1234...abcd",
        }],
    });
    ```
  </Tab>

  <Tab title="Node.js">
    ```typescript theme={null}
    import { CrossmintWallets, createCrossmint } from "@crossmint/wallets-sdk";

    const crossmint = createCrossmint({
        apiKey: "YOUR_SERVER_API_KEY",
    });
    const crossmintWallets = CrossmintWallets.from(crossmint);

    const wallet = await crossmintWallets.createWallet({
        chain: "base-sepolia",
        recovery: { type: "email", email: "user@example.com" },
        signers: [{
            type: "external-wallet",
            address: "0x1234...abcd",
        }],
    });
    ```
  </Tab>
</Tabs>

## Signing Transactions

External wallet signing requires an `onSign` callback. Before sending transactions, activate the signer with the full config:

```typescript theme={null}
wallet.useSigner({
    type: "external-wallet",
    address: "0x1234...abcd",
    onSign: async (payload) => {
        // EVM: payload is a hex-encoded message; return a hex-encoded signature
        // Solana: payload is a VersionedTransaction; return the signed transaction
        // Stellar: payload is a string; return a signed string
        return await externalWallet.signMessage(payload);
    },
});

const { hash } = await wallet.send(
    "0xRecipientAddress",
    "usdc",
    "10"
);
```

See [Add Signers — External Wallet `onSign` by Chain](/wallets/guides/signers/add-signers#external-wallet-onsign-by-chain) for chain-specific `onSign` signatures and return values.

## Adding an External Wallet to an Existing Wallet

If the wallet already exists with a different signer, you can register an external wallet via `wallet.addSigner({ type: "external-wallet", address })`. See [Add Signers](/wallets/guides/signers/add-signers#add-an-external-wallet-signer) for the full flow.

## Next Steps

<CardGroup cols={3}>
  <Card title="Add Signers" icon="key" href="/wallets/guides/signers/add-signers">
    Register additional signers on an existing wallet
  </Card>

  <Card title="Configure Recovery" icon="shield-halved" href="/wallets/guides/signers/configure-recovery">
    Set up email or phone recovery
  </Card>

  <Card title="Device Signer" icon="microchip" href="/wallets/guides/signers/device-signer">
    The default client-side signer
  </Card>
</CardGroup>