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

# Domain

> TypeScript utilities for constructing EIP-712 typed data domains for CoW Protocol order signing

# Domain

The domain module supplies utilities for constructing EIP-712 typed data domains necessary for signing CoW Protocol orders.

## domain()

Generates the Gnosis Protocol v2 domain structure used in order signing.

```typescript theme={null}
function domain(
  chainId: number,
  verifyingContract: string
): TypedDataDomain
```

**Parameters:**

| Name                | Type     | Description                                                    |
| ------------------- | -------- | -------------------------------------------------------------- |
| `chainId`           | `number` | The EIP-155 chain identifier where the contract operates       |
| `verifyingContract` | `string` | The GPv2Settlement contract address for signature verification |

**Returns:** A `TypedDataDomain` object containing:

* `name`: `"Gnosis Protocol"`
* `version`: `"v2"`
* `chainId`: Supplied chain ID
* `verifyingContract`: Settlement contract address

## Example

```typescript theme={null}
import { domain } from "@cowprotocol/contracts";

const settlementDomain = domain(
  1, // Ethereum mainnet
  "0x9008D19f58AAbD9eD0D60971565AA8510560ab41"
);

console.log(settlementDomain);
// {
//   name: "Gnosis Protocol",
//   version: "v2",
//   chainId: 1,
//   verifyingContract: "0x9008D19f58AAbD9eD0D60971565AA8510560ab41"
// }
```

## TypedDataDomain Interface

```typescript theme={null}
interface TypedDataDomain {
  name?: string;
  version?: string;
  chainId?: number;
  verifyingContract?: string;
  salt?: string;
}
```

## Purpose

The domain structure prevents order replay across different chains and contract instances by being incorporated into all EIP-712 signatures. Always use the correct chain ID and settlement contract address for your target network.

## Common Chain IDs

| Network          | Chain ID |
| ---------------- | -------- |
| Ethereum Mainnet | 1        |
| Gnosis Chain     | 100      |
| Arbitrum One     | 42161    |
| Optimism         | 10       |
| Polygon          | 137      |
| BSC              | 56       |
| Base             | 8453     |
| Avalanche        | 43114    |
| Sepolia          | 11155111 |