What does "extendable-output function" actually mean?

Unlike SHA-256 or SHA3-256, which always produce a fixed-size digest no matter what, an XOF like SHAKE lets you request however many output bytes you want, 16 bytes, 64 bytes, 1000 bytes, from the same underlying sponge construction. Under the hood it's the same Keccak sponge SHA-3 uses, just "squeezed" for as long as you ask instead of a fixed number of rounds.

Why does this tool default to 64 bytes instead of some other length?

64 bytes (512 bits) is double SHA3-256's typical 32-byte output, and it's a common, round default length people reach for when they want "more than usual" output without picking an unusual number. SHAKE256 itself has no fixed output size, this is simply this tool's chosen default, not a property of the algorithm.

What's the difference between SHAKE128 and SHAKE256?

The number refers to the claimed security strength in bits (128 vs. 256), which determines the sponge's internal rate/capacity split, not the output length, both can produce output of any length you request. SHAKE256 has a larger security margin and is the more commonly used default; this tool specifically computes SHAKE256.

Does this tool send my text to a server?

No. The SHAKE256 digest is computed entirely in your browser using @noble/hashes, an audited JavaScript library, so nothing you type here is transmitted anywhere.

SHAKE Hash Calculator - SHAKE256 Extendable-Output Hash Online

Overview

Introduction

Every other hash tool in this category produces one fixed-size output no matter what you ask for. SHAKE is different: it's an extendable-output function, part of the same FIPS 202 SHA-3 standard, that produces however many output bytes you need from one sponge construction.

This tool computes SHAKE256 with a 64-byte (512-bit) default output length, entirely in your browser, useful anywhere you need a variable-length pseudorandom digest rather than a fixed-size hash.

What Is SHAKE Hash Calculator?

SHAKE (Secure Hash Algorithm KECCAK) is a family of extendable-output functions standardized alongside SHA3-224/256/384/512 in FIPS 202, built on the identical Keccak sponge construction.

SHAKE128 and SHAKE256 differ in claimed security strength (128 vs. 256 bits), not output length; both can be "squeezed" for any number of output bytes you request, which is precisely what makes them XOFs rather than conventional fixed-digest hash functions.

How SHAKE Hash Calculator Works

Your UTF-8 text is absorbed into a Keccak sponge at the rate corresponding to SHAKE256's 256-bit security level, using SHAKE's own domain-separated padding (distinct from both raw Keccak's and standard SHA-3's padding bytes).

The sponge is then squeezed for exactly 64 bytes (512 bits) by default, hex-encoded into the output this tool returns, longer than any fixed-size SHA-2 or SHA-3 digest in this category except SHA-512/SHA3-512.

When To Use SHAKE Hash Calculator

Use SHAKE when you specifically need a variable-length pseudorandom output derived from input data, key derivation schemes, generating a longer digest than a fixed hash provides, or protocols that explicitly call for SHAKE128/SHAKE256.

For a conventional fixed-size integrity checksum, this category's SHA3-256 or SHA-256 tools are the more standard, broadly expected choice.

Often used alongside SHA3-256 Hash Calculator, SHA-3 Hash Calculator and Keccak Hash Calculator.

Features

Advantages

Flexible output length from a single, well-analyzed sponge construction, rather than needing a different algorithm per desired length.
Built on the same Keccak permutation and FIPS 202 standard as SHA-3, inheriting its security analysis and NIST endorsement.
Useful as a building block for key-derivation and deterministic random-generation schemes that need more than 512 bits of fixed hash output.

Limitations

Less commonly recognized than fixed-size hashes like SHA-256, so systems expecting a standard digest size may not accept SHAKE output directly.
The chosen 64-byte default here is this tool's convenience choice, not an inherent property of SHAKE; other tools or specs may expect a different length.
Requires understanding XOFs conceptually, since "the SHAKE256 hash" is ambiguous without also specifying the requested output length.

Examples

Hashing a short greeting to 64 bytes

Input

Hello, world!

Output

cf68a0d388047ed588ad72d3808cf9a3243f04d4901748c705fbf3a27d955542fd9d53af53e84c8abd4fce6e224af9a0a9e7eea5573a886b1af8c29f9897c8b5

13 bytes of UTF-8 text produce this tool's default 64-byte (128 hex character) SHAKE256 output, computed directly with @noble/hashes' shake256 and dkLen: 64.

Best Practices & Notes

Best Practices

Always specify the exact output length you're using when documenting or comparing SHAKE results, since the algorithm name alone doesn't determine digest size.
Prefer SHAKE256 over SHAKE128 by default for its larger security margin unless a spec specifically calls for SHAKE128.
For a conventional fixed-size checksum instead, use this category's SHA3-256 or SHA-256 tools.

Developer Notes

Uses @noble/hashes/sha3.js's shake256 export with { dkLen: 64 } to request a fixed 64-byte output, since createHashTransform's hasher signature expects a function that always returns the same shape; a future variable-length-output UI could expose dkLen as a parameter. Verified by computing the digest directly against this exact dependency for known input strings.

SHAKE Hash Calculator Use Cases

Generating a longer-than-usual pseudorandom digest from input data
Studying or reproducing SHAKE256 output as part of a key-derivation or deterministic-randomness scheme
Comparing SHAKE's sponge-based extendable output against fixed-size SHA-3 digests for the same input
Prototyping protocols that specify SHAKE128/SHAKE256 before implementing them in a target language

Common Mistakes

Calling SHAKE256 output "the hash" without specifying the length used; unlike SHA-256, the digest size isn't implied by the algorithm name.
Assuming SHAKE128 and SHAKE256 differ in output length rather than claimed security strength; both can produce any output length.
Expecting SHAKE output to be accepted anywhere a conventional fixed-size hash is required without confirming the receiving system actually supports variable-length XOF output.

Tips

If you need standard SHA-3 output sizes instead, this category's SHA3-256/384/512 tools (or the family-view SHA-3 Hash Calculator) are the closer match.
Remember SHAKE's padding differs from both raw Keccak's and standard SHA-3's, so none of the three will produce matching output for the same input even at the same byte length.

SHAKE Hash Calculator