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

# Adapters

> Connect CoW Protocol SDK with different Ethereum libraries

## Overview

Adapters provide a unified interface for the CoW Protocol SDK to work with different Ethereum libraries. They abstract away library-specific implementations, allowing you to use your preferred web3 library while maintaining consistent SDK functionality.

## Available Adapters

The SDK provides three official adapters:

<CardGroup cols={3}>
  <Card title="Viem" icon="v">
    Modern, lightweight TypeScript library
  </Card>

  <Card title="Ethers v6" icon="6">
    Latest version of the popular Ethers library
  </Card>

  <Card title="Ethers v5" icon="5">
    Legacy Ethers version for existing projects
  </Card>
</CardGroup>

## ViemAdapter

The `ViemAdapter` connects the SDK to [Viem](https://viem.sh), a modern TypeScript Ethereum library with excellent type safety and tree-shaking support.

### Installation

```bash theme={null}
npm install @cowprotocol/sdk-viem-adapter viem
```

### Setup

```typescript theme={null}
import { createPublicClient, http } from 'viem'
import { privateKeyToAccount } from 'viem/accounts'
import { mainnet } from 'viem/chains'
import { ViemAdapter } from '@cowprotocol/sdk-viem-adapter'
import { setGlobalAdapter } from '@cowprotocol/cow-sdk'

// Create a public client (provider)
const publicClient = createPublicClient({
  chain: mainnet,
  transport: http('https://eth-mainnet.g.alchemy.com/v2/YOUR_KEY'),
})

// Create an account from private key
const account = privateKeyToAccount('0x...')

// Create the adapter
const adapter = new ViemAdapter({
  provider: publicClient,
  signer: account,
})

// Set as global adapter
setGlobalAdapter(adapter)
```

### Using with WalletClient

If you already have a `WalletClient` (e.g., from Wagmi or RainbowKit):

```typescript theme={null}
import { createWalletClient, custom } from 'viem'
import { ViemAdapter } from '@cowprotocol/sdk-viem-adapter'

const walletClient = createWalletClient({
  chain: mainnet,
  transport: custom(window.ethereum),
})

const adapter = new ViemAdapter({
  provider: publicClient,
  walletClient,
})
```

## EthersV6Adapter

The `EthersV6Adapter` integrates with Ethers.js v6, the latest major version with improved TypeScript support and modern JavaScript features.

### Installation

```bash theme={null}
npm install @cowprotocol/sdk-ethers-v6-adapter ethers@^6
```

### Setup

```typescript theme={null}
import { JsonRpcProvider, Wallet } from 'ethers'
import { EthersV6Adapter } from '@cowprotocol/sdk-ethers-v6-adapter'
import { setGlobalAdapter } from '@cowprotocol/cow-sdk'

// Create provider
const provider = new JsonRpcProvider('https://eth-mainnet.g.alchemy.com/v2/YOUR_KEY')

// Create wallet
const wallet = new Wallet('0x...', provider)

// Create adapter
const adapter = new EthersV6Adapter({
  provider,
  signer: wallet,
})

setGlobalAdapter(adapter)
```

### Using RPC URL Directly

You can pass an RPC URL string instead of a provider instance:

```typescript theme={null}
const adapter = new EthersV6Adapter({
  provider: 'https://eth-mainnet.g.alchemy.com/v2/YOUR_KEY',
  signer: wallet,
})
```

### Browser Wallet Integration

```typescript theme={null}
import { BrowserProvider } from 'ethers'

const provider = new BrowserProvider(window.ethereum)
const signer = await provider.getSigner()

const adapter = new EthersV6Adapter({
  provider,
  signer,
})
```

## EthersV5Adapter

The `EthersV5Adapter` supports Ethers.js v5 for projects that haven't migrated to v6.

### Installation

```bash theme={null}
npm install @cowprotocol/sdk-ethers-v5-adapter ethers@^5
```

### Setup

```typescript theme={null}
import { ethers } from 'ethers'
import { EthersV5Adapter } from '@cowprotocol/sdk-ethers-v5-adapter'
import { setGlobalAdapter } from '@cowprotocol/cow-sdk'

// Create provider
const provider = new ethers.providers.JsonRpcProvider(
  'https://eth-mainnet.g.alchemy.com/v2/YOUR_KEY'
)

// Create wallet
const wallet = new ethers.Wallet('0x...', provider)

// Create adapter
const adapter = new EthersV5Adapter({
  provider,
  signer: wallet,
})

setGlobalAdapter(adapter)
```

### Browser Integration (v5)

```typescript theme={null}
const provider = new ethers.providers.Web3Provider(window.ethereum)
const signer = provider.getSigner()

const adapter = new EthersV5Adapter({
  provider,
  signer,
})
```

## Adapter Interface

All adapters implement a common interface from `@cowprotocol/sdk-common`:

<CodeGroup>
  ```typescript Common Methods theme={null}
  // Get network chain ID
  await adapter.getChainId()

  // Get contract bytecode
  await adapter.getCode(address)

  // Get transaction receipt
  await adapter.getTransactionReceipt(hash)

  // Read contract data
  await adapter.readContract({
    address: contractAddress,
    abi: contractAbi,
    functionName: 'balanceOf',
    args: [userAddress],
  })

  // Get contract instance
  const contract = adapter.getContract(address, abi)
  ```

  ```typescript Signer Methods theme={null}
  // Access the signer
  const signer = adapter.signer

  // Get signer address
  const address = await signer.getAddress()

  // Sign typed data (EIP-712)
  const signature = await signer.signTypedData(
    domain,
    types,
    message
  )

  // Send transaction
  const tx = await signer.sendTransaction({
    to: recipientAddress,
    value: amount,
  })
  ```
</CodeGroup>

## Dynamic Signer Management

All adapters support changing the signer after initialization:

```typescript theme={null}
// Create adapter without signer
const adapter = new ViemAdapter({ provider: publicClient })
setGlobalAdapter(adapter)

// Later, set the signer
const account = privateKeyToAccount('0x...')
adapter.setSigner(account)
```

## Choosing an Adapter

<AccordionGroup>
  <Accordion title="Use ViemAdapter when...">
    * Starting a new project with modern TypeScript
    * Bundle size is a concern (Viem is smaller)
    * You want the best TypeScript experience
    * Using Next.js, Wagmi, or RainbowKit
  </Accordion>

  <Accordion title="Use EthersV6Adapter when...">
    * You're already using Ethers v6 in your project
    * You need the latest Ethers features
    * Migrating from v5 to v6
  </Accordion>

  <Accordion title="Use EthersV5Adapter when...">
    * You have an existing project on Ethers v5
    * Dependencies require Ethers v5
    * You're not ready to migrate to v6
  </Accordion>
</AccordionGroup>

## Best Practices

<CardGroup cols={2}>
  <Card title="Set Global Adapter Early" icon="bolt">
    Call `setGlobalAdapter()` before initializing any SDK classes to ensure all components use the correct adapter.
  </Card>

  <Card title="Reuse Adapter Instances" icon="recycle">
    Create one adapter instance and reuse it across your application to avoid unnecessary overhead.
  </Card>

  <Card title="Handle Provider Changes" icon="rotate">
    When users switch networks or accounts, update the adapter using `setProvider()` or `setSigner()` methods.
  </Card>

  <Card title="Type Safety" icon="shield-check">
    Leverage TypeScript's type inference with adapters for compile-time safety when working with contract ABIs.
  </Card>
</CardGroup>

## Next Steps

<CardGroup cols={2}>
  <Card title="Order Types" icon="list" href="/concepts/order-types">
    Learn about different order types in CoW Protocol
  </Card>

  <Card title="Trading SDK" icon="code" href="/api-reference/trading-sdk">
    Start building with the Trading SDK
  </Card>
</CardGroup>