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

# Sign Typed Data (EIP-712)

> Sign structured data using the EIP-712 standard

## Method Signature

```typescript theme={null}
align.blockchain.wallets.signTypedData(
  wallet: Wallet,
  domain: TypedDataDomain,
  types: Record<string, TypedDataField[]>,
  value: Record<string, unknown>
): Promise<string>
```

## Parameters

<ParamField body="wallet" type="Wallet" required>
  The wallet to sign with
</ParamField>

<ParamField body="domain" type="TypedDataDomain" required>
  EIP-712 domain separator (name, version, chainId, verifyingContract)
</ParamField>

<ParamField body="types" type="Record<string, TypedDataField[]>" required>
  Type definitions for the data structure
</ParamField>

<ParamField body="value" type="Record<string, unknown>" required>
  The actual data to sign
</ParamField>

## Returns

Returns the signature as a hex string.

## Examples

### ERC-20 Permit (Gasless Approval)

<Tabs>
  <Tab title="TypeScript">
    ```typescript theme={null}
    import Align from "@tolbel/align";
    import type { TypedDataDomain, TypedDataField } from "ethers";

    const align = new Align({
      apiKey: process.env.ALIGN_API_KEY!,
      environment: "sandbox",
    });

    const wallet = await align.blockchain.wallets.createFromPrivateKey(
      process.env.PRIVATE_KEY!
    );

    // EIP-712 Domain for USDC on Polygon
    const domain: TypedDataDomain = {
      name: "USD Coin",
      version: "1",
      chainId: 137,
      verifyingContract: "0x2791Bca1f2de4661ED88A30C99A7a9449Aa84174",
    };

    // Permit type structure
    const types: Record<string, TypedDataField[]> = {
      Permit: [
        { name: "owner", type: "address" },
        { name: "spender", type: "address" },
        { name: "value", type: "uint256" },
        { name: "nonce", type: "uint256" },
        { name: "deadline", type: "uint256" },
      ],
    };

    // Permit data
    const value = {
      owner: wallet.address,
      spender: "0xSpenderContract...",
      value: "1000000000", // 1000 USDC
      nonce: 0,
      deadline: Math.floor(Date.now() / 1000) + 3600, // 1 hour
    };

    const signature = await align.blockchain.wallets.signTypedData(
      wallet,
      domain,
      types,
      value
    );

    console.log(`Permit signature: ${signature}`);
    // Use with permit() function for gasless approval
    ```
  </Tab>
</Tabs>

### NFT Minting Signature

```typescript theme={null}
const domain = {
  name: "MyNFT",
  version: "1",
  chainId: 1,
  verifyingContract: NFT_CONTRACT_ADDRESS,
};

const types = {
  MintRequest: [
    { name: "to", type: "address" },
    { name: "tokenId", type: "uint256" },
    { name: "uri", type: "string" },
  ],
};

const value = {
  to: wallet.address,
  tokenId: 123,
  uri: "ipfs://QmHash...",
};

const signature = await align.blockchain.wallets.signTypedData(
  wallet,
  domain,
  types,
  value
);
```

<Info>
  EIP-712 signatures are human-readable in wallet UIs, showing users exactly
  what they're signing.
</Info>

<Warning>
  **Always verify the domain** matches the expected contract. Malicious domains
  can trick users into signing harmful transactions.
</Warning>

## Related Methods

<CardGroup cols={2}>
  <Card title="Sign Message" icon="signature" href="/docs/api/blockchain/wallets/sign-message">
    Sign raw messages
  </Card>

  <Card title="Create Wallet" icon="wallet" href="/docs/api/blockchain/wallets/create">
    Create new wallet
  </Card>
</CardGroup>