> For the complete documentation index, see [llms.txt](https://docs.megaeth.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.megaeth.com/moss-docs/methods/methods/sign-data.md).

# mega.signData()

Sign structured data through the wallet approval surface — typically EIP-712 typed payloads for permits, structured approvals, or attestations. For plain string signing use [`signMessage()`](/moss-docs/methods/methods/sign-message.md).

## Signature

`mega.signData(request: SignDataRequest): Promise<SignDataResponse>`

## Parameters

| Field  | Type  | Required | Notes                                                                                     |
| ------ | ----- | -------- | ----------------------------------------------------------------------------------------- |
| `data` | `any` | required | Structured payload. For EIP-712, include `domain`, `types`, `primaryType`, and `message`. |

## Example

EIP-712 typed payload:

```typescript
const typed = await mega.signData({
  data: {
    domain: {
      name: 'MyApp',
      version: '1',
      chainId: 4326,
      verifyingContract: '0xContractAddress',
    },
    primaryType: 'Permit',
    types: {
      Permit: [
        { name: 'owner', type: 'address' },
        { name: 'spender', type: 'address' },
        { name: 'value', type: 'uint256' },
      ],
    },
    message: {
      owner: '0xOwnerAddress',
      spender: '0xSpenderAddress',
      value: '1000000',
    },
  },
});

if (typed.status === 'success') {
  console.log(typed.signature);
}
```

## Response

```typescript
type SignDataResponse = {
  status: 'success' | 'cancelled' | 'error';
  error?: string;
  signature?: string;
};
```

## Notes

* User rejection resolves with `cancelled` — treat as neutral.
* Reconnect disconnected wallets before signing.
* Verify signatures server-side before issuing app sessions — see [Server Verify](/moss-docs/wallet/server-verify.md).


---

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