# Sign a message (/guides/signing)



`signMessage` lives on the wallet half of the adapter. It takes the message
bytes and an optional `account` to sign with a specific exposed address.

```ts
signMessage(
  msg: Uint8Array,
  account?: Account,
): Promise<{ signature: Uint8Array; signedMessage: Uint8Array }>;
```

## EVM (and via butr's adapter) [#evm-and-via-butrs-adapter]

The `demo-vite` reference signs per account straight off the connector:

```tsx
const canSign = wallet.connector.capabilities.signMessage;

const handleSign = async () => {
  const bytes = new TextEncoder().encode("Hello from the butr demo");
  await wallet.connector.signMessage(bytes, account);
};

{
  canSign ? <button onClick={() => void handleSign()}>Sign</button> : null;
}
```

Always gate the affordance on `capabilities.signMessage`.

## Solana / Wallet Standard [#solana--wallet-standard]

When you've bridged into a Solana library you'll often call the wallet's
feature directly. The pattern from `demo-with-solana-kit`:

```ts
const feature = walletStd.features["solana:signMessage"];
if (!feature) throw new Error("Wallet does not advertise solana:signMessage");
const account = walletStd.accounts[0];
const [output] = await feature.signMessage({ account, message });
// output.signature is a Uint8Array
```

<Callout type="warn">
  Verify the signature against the returned `signedMessage`, **not** your input bytes. Solana Wallet
  Standard wallets may prefix or re-encode the message internally. EVM wallets echo the input, so
  there it's the same bytes — but writing verification against `signedMessage` works for both.
</Callout>

## Signing through an integration library [#signing-through-an-integration-library]

If you've wired viem / wagmi (see [Integrations](/integrations/viem)),
sign through that library's API instead — it uses the same underlying provider
butr handed you:

```ts
// viem
const sig = await walletClient.signMessage({ account, message: "Hello" });
// wagmi
const sig = await signMessage(wagmiConfig, { message: "Hello" });
```

<Callout type="info">
  **Source:** `AccountRow` in `apps/demo-vite/src/app.tsx`; `handleSign` in
  `apps/demo-with-solana-kit/src/app.tsx` and `apps/demo-with-viem/src/app.tsx`.
</Callout>