Hash calculator

What is a cryptographic hash?

A cryptographic hash function maps an input of any size to a fixed-length output called a digest. This tool implements MD5 (128-bit output), SHA-1 (160-bit), and the SHA-2 family: SHA-256, SHA-384, and SHA-512, named for output bit length.

A useful hash is deterministic, fast, one-way (you cannot recover the input from the digest), and exhibits the avalanche property: flipping a single input bit changes roughly half the output bits. Different uses (integrity checks, signatures, content addressing) rely on different subsets of these properties.

How it works

Each algorithm processes the input in fixed-size blocks, mixing them through a compression function until the entire input is absorbed. SHA-1 produces 20 bytes, SHA-256 produces 32 bytes, SHA-512 produces 64 bytes. The output is conventionally written as lowercase hex.

SHA-1, SHA-256, SHA-384, and SHA-512 are available natively in the browser through the Web Crypto API's crypto.subtle.digest(). MD5 has no native support, because every modern platform considers it broken. It is computed here by a small in-browser implementation, for legacy interoperability.

When to use this tool

• Verifying a downloaded file against the publisher's checksum.
• Computing a content-addressed identifier for caching, deduplication, or rsync-style change detection.
• Generating an ETag for an HTTP response.
• Checking that two strings or files are byte-identical when only the digests are practical to share.
• Inspecting a known-good signature input before producing or verifying a digital signature.

Common pitfalls

• Never use these for password hashing. Argon2id, bcrypt, or scrypt are designed to be slow and memory-hard. Raw cryptographic hashes are fast on purpose, which is the wrong property against an attacker brute-forcing a stolen database.
• MD5 and SHA-1 are broken for collision resistance. Researchers can construct two inputs that hash to the same value (SHA-1 chosen-prefix collisions were demonstrated in 2017). Do not rely on either to detect intentional tampering.
• Length-extension attacks affect MD5, SHA-1, SHA-256, and SHA-512. Constructions like hash(secret || message) let an attacker append data without the secret. Use HMAC-SHA-256 instead.
• Hex case matters in string comparisons. Lowercase is conventional; a tool that uppercases will not byte-equal one that does not, even for the same digest.
• Hashing a string requires committing to an encoding (almost always UTF-8). Tools that disagree on encoding produce different digests for the same visible string.

Frequently asked

Which hash should I use?

SHA-256 for general integrity work. SHA-512 if you need the larger digest. HMAC-SHA-256 for message authentication. Argon2id, bcrypt, or scrypt for passwords, never a raw hash.

Is SHA-256 still secure?

Yes. No practical collision attack exists against SHA-256 as of 2026, and the NSA-designed SHA-2 family remains the default in TLS, code signing, and most modern protocols.

Can I still use MD5 for anything?

For non-adversarial integrity checks (cache keys, deduplication keys, accidental-corruption detection), yes. Anywhere an attacker might engineer a collision, no.

Why does my checksum differ from another tool?

Common causes: line-ending normalization (CRLF versus LF), text-mode encoding mismatch (UTF-8 versus UTF-16), or a stray trailing newline. Compare bytes, not visible text.

Does this work on large files?

Yes. Hashing happens in your browser, so memory is the only limit. Multi-gigabyte inputs may be slow but will not leave the device.