Is Keccak-256 the same as SHA3-256?

No. Keccak-256 uses the original Keccak padding (0x01), while the NIST SHA3-256 standard uses a different domain separation byte (0x06). Ethereum adopted Keccak before the NIST standard was finalized, so the outputs differ for the same input. This tool produces the Ethereum-compatible Keccak-256 output.

Does this tool send my input to a server?

No. The entire hash computation runs in your browser using the ethereum-cryptography JavaScript library. Your input text never leaves your device.

Why does the hash start with 0x?

In Ethereum and Solidity conventions, hex strings are prefixed with "0x" to distinguish them from decimal numbers. The raw hash is 32 bytes (64 hex characters). Toggle the prefix option to copy with or without it.

Can I use this to compute Solidity keccak256(abi.encodePacked(...)) outputs?

Yes, for string and bytes inputs. abi.encodePacked of a single string argument is identical to the raw UTF-8 bytes of that string, so hashing the same text here will match keccak256(abi.encodePacked(myString)) in Solidity.

What is the output length?

Keccak-256 always produces a 256-bit (32-byte) output, represented as 64 hexadecimal characters. With the 0x prefix it is 66 characters total.

Is the computation deterministic?

Yes. The same input bytes always produce the same 64-character hex digest. The algorithm is a deterministic one-way function.

Keccak-256 Hash Generator

Name: Keccak-256 Hash Generator
Availability: InStock
Author: Nham Vu

Instantly compute the Keccak-256 hash of any text — the same algorithm Ethereum and Solidity use for address derivation and data integrity.

Input Text

Multi-line mode

Include 0x prefix

0 characters · 0 bytes

Keccak-256 Hash

Ethereum-compatible

Enter text on the left to compute its hash

Copied!

Summary

Instantly compute the Keccak-256 hash of any text — the same algorithm Ethereum and Solidity use for address derivation and data integrity.

How it works

Type or paste any text into the input field.
The Keccak-256 hash is computed instantly in your browser using the ethereum-cryptography library.
The 64-character hex digest appears in the output panel (with or without the 0x prefix).
Toggle the "Include 0x prefix" option to match Solidity/Web3 formatting.
Click "Copy Hash" to copy the result to your clipboard.
Switch to multi-line mode to hash each line separately for batch processing.

Use cases

Verify Solidity keccak256() output before deploying a smart contract.
Derive Ethereum function selectors (first 4 bytes of the hash of the signature).
Debug Web3.js or ethers.js keccak256 calls during dApp development.
Generate deterministic identifiers for data in blockchain applications.
Check data integrity by comparing hashes before and after transfer.
Learn how Ethereum internally computes address checksums and event topics.
Quickly hash ABI-encoded function signatures for low-level contract calls.
Generate test vectors for Keccak-256 unit tests in any language.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu