sign-solana-message

name	sign-solana-message
description	Sign an arbitrary message on Solana using MetaMask Connect. Covers both the React wallet-adapter approach (useWallet) and the vanilla browser approach (wallet-standard features).

Sign Solana Message with MetaMask

When to use

Use this skill when:

• Signing an arbitrary message on Solana with MetaMask Connect
• Implementing sign-in-with-Solana or message verification flows
• Using useWallet().signMessage in a React app
• Using the solana:signMessage wallet-standard feature in a vanilla browser app

Workflow

Step 1: Encode the message

Solana message signing requires a Uint8Array. Use TextEncoder to convert a string:

const message = new TextEncoder().encode('Sign this message to verify your identity');

Step 2a: Sign with React wallet-adapter (useWallet)

Prerequisites: createSolanaClient has been awaited before rendering, WalletProvider is configured with wallets={[]}, and the user is connected. See the setup-solana-react-app skill.

import { useWallet } from '@solana/wallet-adapter-react';

function SignMessageButton() {
  const { signMessage, publicKey, connected } = useWallet();

  const handleSign = async () => {
    if (!signMessage || !publicKey) {
      console.error('Wallet does not support signMessage or is not connected');
      return;
    }

    try {
      const message = new TextEncoder().encode('Hello from MetaMask on Solana!');
      const signature = await signMessage(message);
      console.log('Signature (bytes):', signature);
      console.log('Signature (hex):', Buffer.from(signature).toString('hex'));
      console.log('Signer:', publicKey.toBase58());
    } catch (err: any) {
      if (err.code === 4001) {
        console.log('User rejected the signature request');
        return;
      }
      console.error('signMessage failed:', err);
    }
  };

  return (
    <button onClick={handleSign} disabled={!connected || !signMessage}>
      Sign Message
    </button>
  );
}

Step 2b: Sign with vanilla browser (wallet-standard feature)

Prerequisites: createSolanaClient has been called and the wallet is connected via standard:connect. See the setup-solana-browser-app skill.

import { createSolanaClient } from '@metamask/connect-solana';

const solanaClient = await createSolanaClient({
  dapp: { name: 'My DApp', url: window.location.href },
});

const wallet = solanaClient.getWallet();

// Connect first
const connectFeature = wallet.features['standard:connect'];
const { accounts } = await connectFeature.connect();
const account = accounts[0];

// Sign the message
const signMessageFeature = wallet.features['solana:signMessage'];

try {
  const message = new TextEncoder().encode('Hello from MetaMask on Solana!');

  const [{ signature }] = await signMessageFeature.signMessage({
    account,
    message,
  });

  console.log('Signature (hex):', Buffer.from(signature).toString('hex'));
  console.log('Signer:', account.address);
} catch (err: any) {
  if (err.code === 4001) {
    console.log('User rejected the signature request');
  } else {
    console.error('signMessage failed:', err);
  }
}

Step 3: Verify the signature (optional)

Use tweetnacl or @noble/ed25519 to verify the signature off-chain:

import nacl from 'tweetnacl';

const message = new TextEncoder().encode('Hello from MetaMask on Solana!');
const isValid = nacl.sign.detached.verify(
  message,
  signature, // Uint8Array from signMessage
  publicKey.toBytes(), // Uint8Array of the signer's public key
);
console.log('Signature valid:', isValid);

Step 4: Error handling

Handle these common error scenarios:

Error	Cause	Action
Code 4001	User rejected the request in MetaMask	Show retry UI, do not treat as app error
signMessage is undefined	Wallet does not support message signing	Check signMessage exists before calling
publicKey is null	Wallet not connected	Prompt user to connect first
Network error	MetaMask Mobile connection interrupted	Retry or reconnect

try {
  const signature = await signMessage(message);
} catch (err: any) {
  switch (err.code) {
    case 4001:
      // User rejected — show retry button
      break;
    case -32002:
      // Request already pending — wait for user to act in MetaMask
      break;
    default:
      console.error('Unexpected error:', err);
  }
}

Important Notes

• Messages must be Uint8Array — use new TextEncoder().encode(string) to convert. Do not pass raw strings to signMessage.
• signMessage may be undefined — always check that signMessage exists on the wallet adapter before calling it. Not all wallets support arbitrary message signing.
• The signature is Ed25519 — Solana uses Ed25519 signatures. The returned Uint8Array is 64 bytes.
• User rejection is code 4001 — handle it gracefully with a retry option. Do not log it as an error.
• Wallet name is "MetaMask" — case-sensitive, used to identify the MetaMask wallet in the adapter list.
• Solana networks — mainnet, devnet, and testnet scopes are all modeled by the SDK; non-mainnet availability depends on the connected MetaMask build/version, so handle connection errors rather than assuming a cluster is present.