web3_sha3 | zkSync Era RPC Docs

Compute the Keccak-256 hash of given data on zkSync Era. Useful for hash verification, smart contract development, and data integrity checks.

Returns the Keccak-256 hash (not standard SHA3-256) of the given data on zkSync Era.

Why zkSync? Build on Matter Labs' flagship zkEVM powering the Elastic Network of interoperable hyperchains with ZK Stack modular framework, hyperchain interoperability, native account abstraction, and $1.9B in tokenized real-world assets.

Important: Despite the method name, web3_sha3 computes Keccak-256, which differs from the NIST-standardized SHA3-256. Ethereum adopted Keccak before NIST finalized the SHA-3 standard with different padding.

When to Use This Method

web3_sha3 is helpful for ZK developers, RWA tokenization teams, and builders launching custom L2/L3 chains:

Hash Verification — Confirm that your local Keccak-256 implementation matches the node's output
Smart Contract Development — Compute function selectors and event topic hashes needed for ABI encoding
Data Integrity Checks — Hash data server-side via RPC and compare against expected values
Debugging — Verify hashing results when troubleshooting transaction or contract interactions

Code Examples

Common Use Cases

1. Function Selector Computation

Compute Solidity function selectors for ABI encoding:

JavaScript

async function getFunctionSelector(provider, signature) {
  // Convert signature to hex
  const hexSignature = '0x' + Buffer.from(signature).toString('hex');

  // Hash via RPC
  const hash = await provider.send('web3_sha3', [hexSignature]);

  // Function selector is the first 4 bytes
  const selector = hash.slice(0, 10);
  console.log(`${signature} => ${selector}`);
  return selector;
}

// Example: compute selectors for common ERC-20 functions
const selectors = {
  'transfer(address,uint256)': await getFunctionSelector(provider, 'transfer(address,uint256)'),
  'balanceOf(address)': await getFunctionSelector(provider, 'balanceOf(address)'),
  'approve(address,uint256)': await getFunctionSelector(provider, 'approve(address,uint256)'),
};

2. Hash Verification Between Local and RPC

Verify your local hashing matches the node to catch library misconfigurations:

JavaScript

async function verifyHashingConsistency(provider) {
  const testCases = [
    { input: '0x', label: 'empty bytes' },
    { input: '0x68656c6c6f', label: '"hello"' },
    { input: '0x0123456789abcdef', label: 'hex data' },
  ];

  for (const { input, label } of testCases) {
    const rpcHash = await provider.send('web3_sha3', [input]);
    const localHash = keccak256(input);

    const match = rpcHash === localHash;
    console.log(`${label}: ${match ? 'PASS' : 'FAIL'}`);

    if (!match) {
      console.error(`  RPC:   ${rpcHash}`);
      console.error(`  Local: ${localHash}`);
    }
  }
}

3. Event Topic Hash Generation

Generate event topic hashes for filtering logs:

Python

from web3 import Web3

def get_event_topic(w3, event_signature):
    """Generate the topic hash for an event signature."""
    hex_sig = '0x' + event_signature.encode().hex()
    result = w3.provider.make_request('web3_sha3', [hex_sig])
    return result['result']

w3 = Web3(Web3.HTTPProvider('https://api-zksync-era-mainnet-full.n.dwellir.com/YOUR_API_KEY'))

# Common ERC-20 event topics
topics = {
    'Transfer(address,address,uint256)': get_event_topic(w3, 'Transfer(address,address,uint256)'),
    'Approval(address,address,uint256)': get_event_topic(w3, 'Approval(address,address,uint256)'),
}

for sig, topic in topics.items():
    print(f'{sig}\n  => {topic}')

Error Handling

Error Code	Description	Solution
-32602	Invalid params	Ensure data is a valid `0x`-prefixed hex string
-32603	Internal error	Retry with exponential backoff
-32005	Rate limit exceeded	Implement rate limiting or compute hashes locally instead

eth_call — Execute a call without creating a transaction
eth_getCode — Get contract bytecode at an address
web3_clientVersion — Get node client version

web3_sha3 - zkSync RPC Method