web3_sha3

web3_sha3 computes the Keccak-256 hash of a piece of hex-encoded data and returns the 32-byte digest. Despite the name "sha3," this is the original Keccak-256 used throughout the EVM, not the later NIST SHA3-256 standard — the two produce different output for the same input. Base is Coinbase's OP Stack optimistic rollup that settles to Ethereum and uses ETH for gas, and because it runs the same EVM as Ethereum, Keccak-256 hashing underpins how its contracts derive event topics, function selectors, and storage slots. Call it at https://base.therpc.io/YOUR_API_KEY on chain ID 8453 (hex 0x2105).

Use cases

• Compute event topic hashes by hashing an event signature like Transfer(address,address,uint256) (hex-encoded) so you can filter Base logs with eth_getLogs for that exact topic.
• Generate 4-byte function selectors by hashing a function signature and taking the first four bytes of the digest, useful when crafting raw calldata for a Base contract call.

Parameters

Response

Example request

1curl https://base.therpc.io/YOUR_API_KEY \
2  -X POST \
3  -H "Content-Type: application/json" \
4  -d '{
5    "jsonrpc": "2.0",
6    "method": "web3_sha3",
7    "params": ["0x"],
8    "id": 1
9  }'

Try it live in the Base playground.

Errors & troubleshooting

Common pitfalls

• The input must be 0x-prefixed hex bytes, not a raw UTF-8 string. To hash text like an event signature, encode the string to hex first; passing the plain string yields the wrong digest or an "invalid argument" error.
• Keccak-256 is not NIST SHA3-256. A standard library "sha3" function will produce a different hash unless it specifically implements the Ethereum/Keccak variant, so verify your local hasher matches web3_sha3 before relying on offline computation for Base.

Supported networks

• Mainnet — Chain ID: 8453
• Sepolia — Chain ID: 84532

See also

• eth_call
• eth_getLogs

1curl https://base.therpc.io/YOUR_API_KEY \
2  -X POST \
3  -H 'Content-Type: application/json' \
4  -d '{"jsonrpc":"2.0","id":1,"method":"web3_sha3","params":["0x"]}'