POST
/
evm
eth_chainId
curl --request POST \
  --url https://hyperliquid-mainnet.core.chainstack.com/4f8d8f4040bdacd1577bff8058438274/evm \
  --header 'Content-Type: application/json' \
  --data '{
  "jsonrpc": "2.0",
  "method": "eth_chainId",
  "params": [],
  "id": 1
}'
{
  "jsonrpc": "2.0",
  "id": 1,
  "result": "0x3e7"
}
The eth_chainId JSON-RPC method returns the chain ID of the currently connected blockchain network. This method is fundamental for identifying the specific blockchain network, ensuring transaction compatibility, and implementing network-specific logic in applications.
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​
Parameters

This method takes no parameters. The params field should be an empty array.

​
Response

The method returns the chain ID as a hexadecimal string.

​
Response structure

Chain identification:
  • result — The chain ID as a hexadecimal string (e.g., “0x3e7” which equals 999 in decimal for Hyperliquid mainnet)

​
Chain ID interpretation

Hexadecimal format:
  • Chain IDs are returned in hexadecimal format with “0x” prefix
  • Convert to decimal for human-readable chain identification
  • Examples: “0x3e7” = 999 in decimal (Hyperliquid mainnet); “0x3e6” = 998 (Hyperliquid testnet)
Network identification:
  • Each blockchain network has a unique chain ID
  • Essential for preventing replay attacks across different networks
  • Used by wallets and applications for network validation

​
Usage example

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Basic implementation

// Get Hyperliquid chain ID
const getChainId = async () => {
  const response = await fetch('https://hyperliquid-mainnet.core.chainstack.com/YOUR_ENDPOINT/evm', {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
    },
    body: JSON.stringify({
      jsonrpc: '2.0',
      method: 'eth_chainId',
      params: [],
      id: 1
    })
  });
  
  const data = await response.json();
  const chainId = parseInt(data.result, 16);
  
  return {
    hex: data.result,
    decimal: chainId,
    network: chainId === 999 ? 'Hyperliquid Mainnet' : chainId === 998 ? 'Hyperliquid Testnet' : 'Unknown'
  };
};

// Verify network connection
const verifyNetwork = async () => {
  const { decimal: chainId, network } = await getChainId();
  
  if (chainId !== 999) {
    throw new Error(`Expected Hyperliquid Mainnet (999), got ${network} (${chainId})`);
  }
  
  console.log(`Connected to ${network}`);
  return true;
};

// Usage
verifyNetwork()
  .then(() => console.log('Network verified'))
  .catch(error => console.error('Network verification failed:', error));

​
Network identification

​
Hyperliquid chain IDs

Chain details:
  • Mainnet: 999 (0x3e7 in hexadecimal)
  • Testnet: 998 (0x3e6 in hexadecimal)
  • Used for transaction signing and replay protection
Security considerations:
  • Always verify chain ID matches expected network (998)
  • Chain ID prevents transaction replay across different networks
  • Essential for secure transaction processing on Hyperliquid

​
Example request

Shell
curl -X POST \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","method":"eth_chainId","params":[],"id":1}' \
  https://hyperliquid-mainnet.core.chainstack.com/4f8d8f4040bdacd1577bff8058438274/evm

​
Use cases

The eth_chainId method is essential for applications that need to:
  • Network verification: Verify connection to Hyperliquid Mainnet (chain ID 998)
  • Transaction security: Ensure transactions are signed with correct chain ID for replay protection
  • Wallet configuration: Configure wallets to recognize and connect to Hyperliquid
  • Application initialization: Verify network connection during application startup
  • Error handling: Provide meaningful error messages for network mismatches
  • Development tools: Build tools that automatically detect the Hyperliquid network
  • Multi-network applications: Support Hyperliquid alongside other EVM networks
  • Security validation: Validate network before executing sensitive operations

Body

application/json
​
jsonrpc
enum<string>
default:2.0
required

JSON-RPC version

Available options:
2.0
​
method
enum<string>
default:eth_chainId
required

The RPC method name

Available options:
eth_chainId
​
id
integer
default:1
required

Request identifier

​
params
any[]

Parameters for the method (empty array for eth_chainId)

Response

200 - application/json

Successful response with the chain ID

​
jsonrpc
string

JSON-RPC version

​
id
integer

Request identifier

​
result
string

The chain ID as a hexadecimal string