The eth_newFilter JSON-RPC method creates a filter object to notify when logs match the specified criteria. This method returns a filter ID that can be used with eth_getFilterChanges and eth_getFilterLogs to retrieve matching logs. Filters are essential for monitoring specific events on the blockchain.
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Parameters

  1. filter_object (object) — The filter criteria object with the following properties:
    • fromBlock (string, optional) — Block number (hexadecimal) or tag (“latest”, “earliest”, “pending”)
    • toBlock (string, optional) — Block number (hexadecimal) or tag (“latest”, “earliest”, “pending”)
    • address (string or array, optional) — Contract address or array of addresses to filter
    • topics (array, optional) — Array of topic hashes to match (supports null wildcards)

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Response

The method returns a filter ID as a hexadecimal string that can be used to retrieve filter results.

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Response structure

Filter ID:
  • Returns a unique filter identifier as a hexadecimal string
  • Use this ID with eth_getFilterChanges to get new matching logs
  • Use this ID with eth_getFilterLogs to get all matching logs
  • Filters have a limited lifetime and may expire

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Filter object options

Block range:
  • fromBlock and toBlock define the block range to monitor
  • Use “latest” to monitor from the current block
  • Use specific block numbers in hexadecimal format
Address filtering:
  • Single address: "0xB7C609cFfa0e47DB2467ea03fF3e598bf59361A5"
  • Multiple addresses: ["0xAddr1", "0xAddr2"]
  • Omit to match logs from any address
Topic filtering:
  • Topics are indexed event parameters
  • Array position corresponds to topic index (topic0, topic1, etc.)
  • Use null as wildcard for any value at that position
  • Empty array [] matches all topics

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Usage example

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Basic implementation

// Create a new filter
const createFilter = async (filterOptions) => {
  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_newFilter',
      params: [filterOptions],
      id: 1
    })
  });
  
  const data = await response.json();
  return data.result;
};

// Monitor specific contract events
const monitorContractEvents = async (contractAddress, eventSignature) => {
  const filter = await createFilter({
    fromBlock: 'latest',
    toBlock: 'latest',
    address: contractAddress,
    topics: [eventSignature] // topic0 is the event signature hash
  });
  
  console.log(`Created filter ${filter} for contract ${contractAddress}`);
  return filter;
};

// Create filter for ERC-20 Transfer events
const monitorTokenTransfers = async (tokenAddress, fromAddress = null, toAddress = null) => {
  // Transfer event signature: Transfer(address,address,uint256)
  const transferSignature = '0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef';
  
  const topics = [transferSignature];
  
  // Add indexed parameters (from and to addresses)
  if (fromAddress) {
    topics.push('0x000000000000000000000000' + fromAddress.slice(2).toLowerCase());
  } else {
    topics.push(null); // Wildcard for any from address
  }
  
  if (toAddress) {
    topics.push('0x000000000000000000000000' + toAddress.slice(2).toLowerCase());
  }
  
  const filter = await createFilter({
    fromBlock: 'latest',
    toBlock: 'latest',
    address: tokenAddress,
    topics: topics
  });
  
  return filter;
};

// Monitor multiple contracts
const monitorMultipleContracts = async (addresses, topics = []) => {
  const filter = await createFilter({
    fromBlock: 'latest',
    toBlock: 'latest',
    address: addresses,
    topics: topics
  });
  
  console.log(`Created multi-contract filter: ${filter}`);
  return filter;
};

// Historical event filter
const createHistoricalFilter = async (fromBlock, toBlock, contractAddress) => {
  const filter = await createFilter({
    fromBlock: `0x${fromBlock.toString(16)}`,
    toBlock: `0x${toBlock.toString(16)}`,
    address: contractAddress,
    topics: []
  });
  
  console.log(`Created historical filter from block ${fromBlock} to ${toBlock}`);
  return filter;
};

// Usage examples
const contractAddress = '0xB7C609cFfa0e47DB2467ea03fF3e598bf59361A5';

// Monitor all events from a contract
monitorContractEvents(contractAddress, null).then(filterId => {
  console.log('Monitor filter created:', filterId);
});

// Monitor token transfers
monitorTokenTransfers(contractAddress).then(filterId => {
  console.log('Transfer filter created:', filterId);
});

// Monitor multiple contracts
const addresses = [
  '0xB7C609cFfa0e47DB2467ea03fF3e598bf59361A5',
  '0xAnother...Address'
];
monitorMultipleContracts(addresses).then(filterId => {
  console.log('Multi-contract filter created:', filterId);
});

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Example request

Shell
curl -X POST \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_newFilter",
    "params": [
      {
        "fromBlock": "latest",
        "toBlock": "latest",
        "address": "0xB7C609cFfa0e47DB2467ea03fF3e598bf59361A5",
        "topics": []
      }
    ],
    "id": 1
  }' \
  https://hyperliquid-mainnet.core.chainstack.com/4f8d8f4040bdacd1577bff8058438274/evm

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Use cases

The eth_newFilter method is essential for applications that need to:
  • Event monitoring: Monitor smart contract events in real-time
  • DeFi applications: Track token transfers, swaps, and other DeFi operations
  • NFT platforms: Monitor NFT minting, transfers, and marketplace activities
  • Trading bots: React to specific blockchain events for automated trading
  • Analytics platforms: Collect event data for analysis and reporting
  • Notification systems: Create alerts based on specific blockchain events
  • Audit tools: Monitor specific contracts for compliance and security
  • DEX monitoring: Track decentralized exchange activities and liquidity events
  • Governance tracking: Monitor DAO governance events and voting
  • Bridge monitoring: Track cross-chain bridge events and transfers
  • Staking applications: Monitor staking rewards and delegation events
  • Oracle monitoring: Track oracle price updates and data feeds
  • Gaming platforms: Monitor in-game transactions and asset transfers
  • Supply chain tracking: Monitor supply chain events and product transfers
  • Insurance platforms: Track insurance claims and policy events
This method provides flexible and efficient event filtering capabilities, enabling real-time blockchain monitoring and event-driven applications on the Hyperliquid EVM platform.