About the Keccak Hash Generator
What is a Keccak hash?
Keccak is the original algorithm that won the NIST SHA-3 competition, before NIST made a small change to the padding to produce the final SHA-3 standard. As a result, Keccak-256 and SHA3-256 give different outputs for the same input. This tool generates the original Keccak, which is the version most people actually need, because it is the hash used throughout Ethereum and the wider blockchain world.
When developers say "keccak256" in the context of smart contracts, tokens or wallet addresses, they mean this original Keccak, not SHA-3. Getting the two mixed up produces hashes that silently fail to match on-chain values, so it is worth being precise. This tool uses a vendored, standards-correct implementation and runs entirely in your browser.
How to Use This Tool
- Enter your input. Type or paste text on the Text tab, or switch to the File tab and drop in a file. The Keccak hash appears instantly.
- Choose the output. Use the Algorithm dropdown to choose the variant. Switch the output between hexadecimal and Base64, and pick upper or lowercase hex.
- Verify a value. Paste a hash you were given into the compare box and the tool tells you instantly whether it matches.
- Copy the result. One click copies the Keccak hash to your clipboard.
Common Use Cases
- Ethereum and smart contracts: Keccak-256 computes function selectors, event topics, storage slots and address checksums; reproduce any of them here.
- Blockchain development: match the keccak256 values your Solidity or web3 code produces.
- Wallet address checksums: the EIP-55 mixed-case checksum is derived from Keccak-256 of the address.
- Verifying on-chain data: confirm a hash you computed matches what a contract expects.
Frequently Asked Questions
What is the difference between Keccak-256 and SHA3-256?
They use the same core but a different padding byte. NIST changed the padding when finalizing SHA-3, so the two produce different digests for identical input. Keccak-256 is the original; SHA3-256 is the NIST standard. They are not interchangeable.
Which one does Ethereum use?
Ethereum uses the original Keccak-256, not the final SHA-3. This is a very common source of bugs: if you hash something with SHA3-256 and compare it to an on-chain value, it will not match. Always use Keccak-256 for anything Ethereum related, which is what this tool defaults to.
Why are there two similar algorithms?
Keccak won the SHA-3 competition, then NIST tweaked the padding before publishing the FIPS 202 standard in 2015. By then Ethereum and other projects had already adopted the original Keccak, so both versions remain in wide use.
How long is a Keccak-256 hash?
Keccak-256 is 256 bits, written as 64 hexadecimal characters. The other variants are 56 (Keccak-224), 96 (Keccak-384) and 128 (Keccak-512) characters. Choose with the Algorithm dropdown.
Is Keccak secure?
Yes. Keccak is cryptographically strong with no known practical attacks, and it resists length-extension attacks. Its security is essentially the same as SHA-3, since they share the same underlying permutation.
Can I hash a file with Keccak?
Yes. Use the File tab and drop in any file; it is hashed locally in your browser and produces the standard Keccak digest.