Is Keccak-256 the same as SHA3-256?

No. Keccak-256 is the original Keccak submission and uses the padding suffix 0x01, while NIST SHA3-256 uses 0x06. The same input gives different digests, so they are not interchangeable.

Why does Ethereum use Keccak-256 instead of SHA3?

Ethereum adopted Keccak-256 before NIST finalised the SHA-3 padding change in FIPS 202, and kept the original variant for compatibility. Solidity's keccak256 and the EVM SHA3 opcode both compute this function.

What is this used for?

Keccak-256 produces Ethereum addresses, transaction and block hashes, ABI function selectors (the first 4 bytes), event topic hashes, and storage slot keys.

Is my text uploaded anywhere?

No. The hash is computed entirely in your browser with a pure-JavaScript Keccak engine, so your input never leaves the page.

What is the Keccak-256 Hash Generator?

Free online Keccak-256 hash generator. Get the original pre-NIST Keccak-256 digest used by Ethereum for any text, computed in your browser with a pure-JS Keccak-f[1600] engine — no upload, no server. It runs free in your browser on Gera Tools, with nothing uploaded.

Keccak-256 Hash Generator

Name: Keccak-256 Hash Generator
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

What this Keccak-256 generator does

This tool computes the original Keccak-256 hash of any text, returning a 256-bit value as 64 hexadecimal characters. This is the exact function used across Ethereum — by Solidity’s keccak256, the EVM SHA3 opcode, address derivation, and ABI function selectors — and it differs from NIST’s SHA3-256.

How it works

Keccak-256 uses the Keccak sponge construction over the Keccak-f[1600] permutation, with a 1088-bit rate (136 bytes) and a 512-bit capacity. The input is padded using the original Keccak rule — append 0x01, zero-pad to 136 bytes, set the last byte’s high bit — then absorbed block-by-block into a 1600-bit state matrix. Each absorption applies 24 rounds of five step mappings: theta (column parity mixing), rho (lane rotation), pi (lane permutation), chi (non-linear mixing), and iota (round constant XOR). After all blocks are absorbed, the first 256 bits are squeezed out as the digest.

The sole difference from FIPS 202 SHA3-256 is the padding suffix byte: Keccak uses 0x01, NIST SHA3-256 uses 0x06. This one-byte change produces entirely different digests for the same input.

Ethereum uses and practical examples

Address derivation

An Ethereum address is derived from a public key by hashing the 64-byte uncompressed public key (without the 0x04 prefix) with Keccak-256 and taking the last 20 bytes (40 hex characters). The EIP-55 checksum then encodes the address with mixed case.

Function selectors

The ABI function selector is the first 4 bytes of the Keccak-256 hash of the function signature. Type it in this tool with no spaces around the commas:

Signature	Keccak-256 first 8 chars (selector)
`transfer(address,uint256)`	`a9059cbb`
`approve(address,uint256)`	`095ea7b3`
`balanceOf(address)`	`70a08231`
`totalSupply()`	`18160ddd`

Event topics

Solidity event signatures are hashed the same way. The topic Transfer(address,address,uint256) hashes to 0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef, which you will recognise as the first topic on any ERC-20 Transfer log.

Storage slots

Mapping slot keys in EVM storage are computed as keccak256(abi.encode(key, slot)), where slot is the mapping’s position in storage. This tool can verify a slot calculation by concatenating the 32-byte key and 32-byte slot number in hex.

Reference values

Input	Keccak-256 digest
(empty)	`c5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470`
`abc`	`4e03657aea45a94fc7d47ba826c8d667c0d1e6e33a64a036ec44f58fa12d6c45`
`hello`	`1c8aff950685c2ed4bc3174f3472287b56d9517b9c948127319a09a7a36deac8`

The empty-string digest is the canonical Ethereum Keccak-256 test vector and differs from SHA3-256’s a7ffc6f8... output for the same reason: the padding byte.

Important: Keccak-256 is not SHA3-256

If you are writing a Solidity contract or parsing Ethereum logs, you need Keccak-256 (0x01 padding), not the NIST SHA3-256 standard (0x06 padding). Many general-purpose cryptography libraries implement SHA3-256 but not the pre-standard Keccak-256. This tool implements the Ethereum-compatible version. If you need the NIST standard, use the SHA3-256 generator instead.