Keccak-256 Hash Generator
Compute the original Keccak hash (Keccak-256 or Keccak-512) of any text — the exact algorithm Ethereum uses, which differs from FIPS SHA-3. Runs entirely in your browser, no server, no sign-up.
About this tool
This Keccak hash generator computes the original Keccak digest of any text right in your browser. The hashing runs locally in WebAssembly — your input is never uploaded to a server, which makes it safe for keys, addresses, and other sensitive strings.
A hash is a fixed-length fingerprint of its input. The same text always produces the same digest, but the digest cannot be reversed back into the original — so hashes are ideal for verifying that data has not changed, fingerprinting content, and deriving identifiers.
Keccak vs. SHA-3 — they are not the same
This tool implements the original Keccak algorithm (the one submitted to the
NIST hash competition), which uses 0x01 multi-rate padding. When Keccak was
standardized as FIPS-202 SHA-3, the padding was changed to 0x06. As a
result, Keccak-256 and SHA3-256 produce completely different digests for the
same input — they are not interchangeable.
- Use Keccak (this tool) when you need the hash that Ethereum and the wider EVM ecosystem use.
- Use SHA-3 (in the Text Hash Generator) when you need the NIST standard.
Where Keccak-256 is used
Keccak-256 is the workhorse hash of Ethereum and EVM-compatible chains:
- Deriving account and contract addresses.
- The EVM
KECCAK256opcode (often writtensha3in older docs). - Hashing transactions, blocks, and storage / Merkle-Patricia trie keys.
- Computing 4-byte function selectors for the contract ABI (the first 4
bytes of
keccak256("transfer(address,uint256)"), etc.).
Supported variants
- Keccak-256 (default) — a 256-bit / 32-byte digest, the Ethereum hash.
- Keccak-512 — a 512-bit / 64-byte digest.
Options
- Variant — choose Keccak-256 or Keccak-512.
- Interpret input as — hash the text as plain UTF-8 (default), or decode it
from hex (a leading
0xis accepted) or base64 first so you can hash existing raw bytes such as a key or calldata. - Output format — return the digest as hex (default) or as base64.
- Uppercase hex — emit the hex digest in uppercase.
Notes
- A hash is a one-way function: a digest cannot be reversed back into the original text.
- For the NIST SHA-3 family (SHA3-256, SHA3-512) and other algorithms (MD5, SHA-1, the SHA-2 family, BLAKE2, BLAKE3), use the Text Hash Generator tool instead.
FAQ
Why is my digest different from a SHA3-256 tool's output?
Because Keccak-256 ≠ SHA3-256. The original Keccak uses 0x01 multi-rate
padding; when NIST standardized it as FIPS-202 SHA-3 the padding changed to
0x06, so the two algorithms give completely different digests for the same
input. This tool is the original Keccak — the one Ethereum uses. For the NIST
SHA-3 variants, use the Text Hash Generator.
How do I hash raw bytes (calldata, a key) instead of a string?
Set Interpret input as to hex or base64. In hex mode a leading 0x is
accepted, so you can paste EVM calldata like 0xa9059cbb… directly and the tool
hashes the decoded bytes, not the literal characters.
How do I compute an Ethereum function selector?
Hash the canonical signature — no spaces, no parameter names — with Keccak-256
and take the first 4 bytes of the digest. For example,
keccak256("transfer(address,uint256)") starts with a9059cbb, the familiar
ERC-20 transfer selector.
Which variant should I pick, Keccak-256 or Keccak-512?
Keccak-256 (the default, 32-byte digest) is what Ethereum and the EVM ecosystem
use everywhere — addresses, storage keys, the KECCAK256 opcode. Keccak-512
gives a 64-byte digest; choose it only when a spec explicitly asks for the
512-bit variant.
Developer & Automation Access
Run it from the terminal
Same engine as this page, headless — via the gizza CLI:
gizza tool keccak-hash "Hello, World!"New to the CLI? Get gizza →
Open it by URL
Pre-fill and auto-run this tool with query parameters — the names match the API/CLI:
https://gizza.ai/tools/keccak-hash/?text=Hello%2C%20World%21&algorithm=keccak-256&input_encoding=text&output_format=hex&uppercase=trueMachine-readable descriptor: tool.json — title + parameters JSON Schema for agents.