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.

Keccak-256 Hash Generator

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 same Keccak sponge and Keccak-f[1600] permutation as SHA3-256, with a 1088-bit rate (136 bytes) and 512-bit capacity. The only difference from FIPS 202 SHA3-256 is the padding: Keccak appends the byte 0x01 as the domain-separation suffix, then zero-pads and ORs 0x80 into the final byte. The message is absorbed block-by-block with 24 rounds of theta, rho, pi, chi, and iota each, and the first 256 bits are squeezed out. To produce a function selector, take the first 4 bytes (8 hex characters) of the Keccak-256 of a signature like transfer(address,uint256). This runs entirely in browser JavaScript with BigInt lane arithmetic.

Tips and notes

The single byte difference in padding (0x01 vs 0x06) is the only thing separating Keccak-256 from SHA3-256.
Example: the empty string hashes to c5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470.
Solidity selector example: keccak256("transfer(address,uint256)") begins with a9059cbb, the well-known ERC-20 transfer selector.
A single changed byte completely changes the digest.