Keccak-256 · Selector
Keccak-256 digests, function selectors and event topics (not the same as SHA3-256).
A free Keccak-256 tool: hash any text or hex data, and derive the 4-byte function selector and 32-byte event topic from a signature. Ethereum uses Keccak-256 specifically. Everything runs locally in your browser.
How to use
- For selectors pick “Function / event signature” and enter e.g. transfer(address,uint256).
- The canonical form, selector and event topic0 are all produced.
- To hash arbitrary data switch to “Hash any data” and enter text or hex.
FAQ
- Are Keccak-256 and SHA3-256 the same?
- No. NIST changed the padding when standardizing Keccak as SHA-3, so the two produce different digests for the same input. Ethereum uses the original Keccak-256; computing a function selector with SHA3-256 gives a wrong value. The site’s Hash tool covers the standard MD5/SHA family.
- How is a function selector computed?
- Take the Keccak-256 of the canonical signature (parameter names and spaces removed, uint written as uint256) and keep the first 4 bytes. For example transfer(address,uint256) → 0xa9059cbb.
- Is any data uploaded?
- No, everything is computed locally.
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