> ## 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.

# Supported Chains

> Learn about the blockchain networks supported by the CoW Protocol Python SDK

## Overview

The CoW Protocol Python SDK provides access to multiple blockchain networks through a `Chain` enum that configures chain IDs, network identifiers, and block explorer URLs.

## Accessing Chain Information

Import the `Chain` enum to retrieve network properties:

```python theme={null}
from cowdao_cowpy.common.chains import Chain

chain = Chain.MAINNET
print(chain.chain_id)      # SupportedChainId.MAINNET
print(chain.name)          # "ethereum"
print(chain.explorer)      # "https://etherscan.io"
```

## Supported Networks

The SDK supports eight blockchain networks:

| Network          | Chain ID | Name          | Explorer             |
| ---------------- | -------- | ------------- | -------------------- |
| Ethereum Mainnet | 1        | ethereum      | etherscan.io         |
| Sepolia Testnet  | 11155111 | sepolia       | sepolia.etherscan.io |
| Gnosis Chain     | 100      | gnosis        | gnosisscan.io        |
| Arbitrum One     | 42161    | arbitrum\_one | arbiscan.io          |
| Base             | 8453     | base          | basescan.org         |
| Polygon          | 137      | polygon       | polygonscan.com      |
| Avalanche        | 43114    | avalanche     | snowtrace.io         |
| BNB Chain        | 56       | bnb           | bscscan.com          |

## Chain Properties

Each `Chain` enum provides three properties:

* **chain\_id** -- Returns the `SupportedChainId` enum value representing the numeric identifier.
* **name** -- Returns the network name as a string for display and configuration.
* **explorer** -- Returns the block explorer URL for transaction and address verification.

## Usage Example

Complete example demonstrating chain specification in a token swap:

```python theme={null}
import os
import asyncio
from dotenv import load_dotenv
from web3 import Account, Web3
from web3.types import Wei
from cowdao_cowpy.cow.swap import swap_tokens
from cowdao_cowpy.common.chains import Chain

load_dotenv()
PRIVATE_KEY = os.getenv("PRIVATE_KEY")
ACCOUNT = Account.from_key(PRIVATE_KEY)

SELL_TOKEN = Web3.to_checksum_address("0xbe72E441BF55620febc26715db68d3494213D8Cb")
BUY_TOKEN = Web3.to_checksum_address("0xfFf9976782d46CC05630D1f6eBAb18b2324d6B14")
AMOUNT = Wei(5000000000000000000)

result = await swap_tokens(
    amount=AMOUNT,
    account=ACCOUNT,
    chain=Chain.SEPOLIA,
    sell_token=SELL_TOKEN,
    buy_token=BUY_TOKEN,
)

print(f"Order UID: {result.uid}")
print(f"Order URL: {result.url}")
```

## Retrieving All Supported Chains

Access the complete list using the `SUPPORTED_CHAINS` constant:

```python theme={null}
from cowdao_cowpy.common.chains import SUPPORTED_CHAINS

for chain in SUPPORTED_CHAINS:
    print(f"{chain.name}: Chain ID {chain.chain_id.value}")
```

<Note>
  The SDK uses chain configuration internally to determine API endpoints, contract addresses, and network-specific parameters.
</Note>