Keccak-256 Hash Generator Online

Q: How long is a Keccak-256 hash?

A Keccak-256 digest is 256 bits, or 32 bytes. It is commonly written as 64 hexadecimal characters. Selecting Base64 changes only the text representation, not the digest length in bytes.

Q: Does Keccak-256 work with Ethereum and Solidity?

Ethereum uses the original Keccak-256 hash function. This tool is useful for comparing digests when the input bytes match. Solidity may hash ABI-encoded values, so hashing a readable string will not necessarily produce the same result as hashing an encoded contract argument.

Q: Can I hash Hex or Base64 data instead of plain text?

Yes. Use Input Encoding to tell the tool how to interpret the input. Hex and Base64 represent bytes, whereas UTF-8 hashes the text itself. For example, UTF-8 abc, Hex 616263, and Base64 YWJj describe the same three input bytes.

Q: What does Enable HMAC-KECCAK_256 do?

It enables HMAC-Keccak-256, a keyed message authentication construction. Unlike a normal hash, HMAC depends on both the message and a secret key. Use it only when the system you are working with specifically expects HMAC-Keccak-256.

Q: Why does my Keccak-256 hash differ from an expected value?

Check the algorithm first: Keccak-256 and SHA3-256 are not interchangeable. Next, confirm the exact input bytes, including UTF-8 versus decoded Hex or Base64, leading and trailing spaces, newlines, and any binary encoding performed by your application.

Q: Can a Keccak-256 hash be decrypted or reversed?

No. Keccak-256 is a one-way hash function, not encryption. A hash can help compare data against a known digest, but it does not contain an encrypted copy of the original message. For passwords, use a purpose-built password-hashing scheme rather than a raw fast hash.

The Keccak-256 Hash Generator calculates a 256-bit hash from text or encoded bytes. Select UTF-8, Hex, or Base64 input, then copy the digest as hexadecimal or Base64 for development, testing, or data checks.

Enable HMAC-KECCAK_256

Auto / Live

Input text

Input Encoding:

Keccak-256 Hash Result

Separator:

Hex (lower)

Hex (UPPER)

Base64

How to Use the Keccak-256 Hash Generator

Use this online Keccak-256 calculator to hash a text string or a sequence of bytes. The result is always a 256-bit digest; the output controls only change how that digest is displayed.

How to Generate a Keccak-256 Hash

Type or paste a string into the Input text editor.
Choose Input Encoding. Keep UTF-8 for ordinary text, or select Hex or Base64 when your input represents encoded bytes.
Under Separator, select Hex (lower), Hex (UPPER), or Base64 for the Keccak-256 Hash Result. These choices change the displayed format, not the underlying digest.
Leave Auto / Live enabled for live updates, or use Run to calculate the hash on demand.
Read the digest in Keccak-256 Hash Result. Select Copy to copy it, or Clear to remove the input and reset the working area.

For example, with Input Encoding set to UTF-8, enter abc. The Keccak-256 digest in Hex (lower):

4e03657aea45a94fc7d47ba826c8d667c0d1e6e33a64a036ec44f58fa12d6c45

Using HMAC-KECCAK_256

Turn on Enable HMAC-KECCAK_256 when you need a keyed message authentication code instead of a regular Keccak-256 digest. HMAC uses a secret key as well as the message, so its output differs from an unkeyed hash.

Switch on Enable HMAC-KECCAK_256 and provide the required key if the tool displays a key-entry control.
Enter your message in Input text, choose Input Encoding and an output format, then read the live result or press Run.

Turn the switch off to return to standard Keccak-256 hashing. HMAC-Keccak-256 is not interchangeable with the unkeyed keccak256() operation used in Ethereum contracts.

What Is Keccak-256?

Keccak-256 is a cryptographic hash function that produces a fixed 256-bit (32-byte) digest from input of any length. In hexadecimal form, that is 64 characters. The same sequence of bytes always produces the same result; changing even one byte generally changes the digest completely.

Keccak belongs to the sponge-based family of algorithms that led to SHA-3. Its original Keccak-256 variant is used in Ethereum-related systems, including smart contract development and cryptographic identifiers.

Keccak-256 vs. SHA3-256

Keccak-256 and the standardized SHA3-256 share the underlying Keccak permutation but use different domain-separation padding. They therefore produce different hashes for identical input. If a protocol, library, or test fixture specifies Keccak-256, substituting a SHA3-256 function will not give the expected result.

For a quick reference, Keccak-256 of the empty byte string is c5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470. The SHA3-256 result for the same empty input begins with a7ffc6f8.

Understanding UTF-8, Hex, and Base64 Input

The selected Input Encoding determines which bytes are hashed. In UTF-8 mode, entering 616263 hashes six text characters. In Hex mode, those characters represent the three bytes for abc. Likewise, YWJj in Base64 represents the same three bytes.

This distinction matters when reproducing known hashes. Use Hex or Base64 input for already-encoded binary data, and UTF-8 for normal text. Match the original data exactly, including whitespace, letter case, and line endings.

Keccak-256 for Ethereum and Development

Ethereum uses the original Keccak-256 variant rather than FIPS SHA3-256. This hash calculator can help reproduce a digest from known input bytes, check development examples, or compare text-based test values.

A smart contract may hash ABI-encoded or packed binary values instead of the characters shown on a screen. To match Solidity keccak256(), first ensure that you are hashing the same byte sequence as the contract; selecting the right algorithm alone is not enough.

Output Formats and Security Notes

Choose Hex (lower) or Hex (UPPER) when a system expects a 64-character hexadecimal digest, or Base64 when you need that same digest represented in Base64. Uppercase and lowercase hexadecimal are alternative spellings of identical bytes.

Important: Hashing is not encryption: there is no decryption step that recovers the original text. A plain Keccak-256 digest is also not a substitute for a dedicated password-hashing algorithm.

Frequently Asked Questions

Is Keccak-256 the same as SHA3-256?

No. Both use the Keccak permutation, but the standardized SHA3-256 algorithm has a different padding suffix. They produce different hashes for the same input, so you must choose the variant required by your application.

How long is a Keccak-256 hash?

Does Keccak-256 work with Ethereum and Solidity?

Can I hash Hex or Base64 data instead of plain text?

What does Enable HMAC-KECCAK_256 do?

Why does my Keccak-256 hash differ from an expected value?

Can a Keccak-256 hash be decrypted or reversed?

Egor Volchenko Developer & Author

Hi! I’m a WordPress developer with over 10 years of experience. I love Tailwind CSS, clean code, and intuitive interfaces. I’m currently working on million.tools — a service with convenient online tools for everyday tasks. I’m building it from scratch with great attention to detail and user experience.

Keccak-256 Hash Generator