Hash Calculator

Hash & HMAC reference

The algorithms exposed by this calculator, what they're actually used for, and the exact commands you can run on your own machine to double-check our output.

Algorithm comparison

How to verify a downloaded file against a published hash

The most common reason people open a hash calculator: confirm that an ISO, installer, or release tarball wasn't corrupted in transit or replaced. Match the page's published hash against the hash of your local file.

# SHA-256 of a file
shasum -a 256 ubuntu-24.04.iso
# Or, on Linux:
sha256sum ubuntu-24.04.iso

# MD5 (legacy)
md5sum file.zip

# SHA-256 — default
Get-FileHash .\file.iso

# Other algorithms
Get-FileHash .\file.iso -Algorithm SHA1
Get-FileHash .\file.iso -Algorithm MD5

certutil -hashfile file.iso SHA256
certutil -hashfile file.iso MD5

Or use the Verifytab above: paste the publisher's hash, drop the file, and we'll auto-detect the algorithm and compare. No data leaves your browser.

HMAC: hashing with a secret key

HMAC (Hash-based Message Authentication Code, RFC 2104) combines a secret key with a message before hashing it. The result proves the message came from someone who knows the key and wasn't altered in transit. It's the basis of:

• Webhook signatures — GitHub, Stripe, Slack all sign delivered payloads with HMAC-SHA256
• JWT HS256 / HS512 — symmetric JSON Web Tokens use HMAC under the hood
• AWS Signature v4 — every signed AWS API request derives an HMAC chain from your secret key
• TOTP / HOTP — 2FA codes (Google Authenticator) are HMAC-SHA1 of a counter

The HMAC tab above accepts a key as plain text or, if it starts with 0x, as a hex string. Use the same key on the sender and receiver — and store keys in a secret manager, not in source code.

SRI (Subresource Integrity) hashes for the web

When you include a third-party script or stylesheet, you can pin its content with an integrity attribute. Browsers refuse to execute the file if its hash doesn't match. SRI hashes are Base64-encoded SHA-256/384/512 with a prefix:

<script
  src="https://cdn.example.com/lib.min.js"
  integrity="sha384-oqVuAfXRKap7fdgcCY5uykM6+R9GqQ8K/uxy9rx7HNQlGYl1kPzQho1wx4JwY8wC"
  crossorigin="anonymous"></script>

Use the Hash tab above with algorithm SHA-384 (or SHA-256/512) and encoding Base64. Prefix the result with sha384- in your HTML.

SHA-2 vs SHA-3: when do you actually need SHA-3?

SHA-2 and SHA-3 are bothcurrently considered secure. They share names like “256-bit” but produce completely different outputs— they aren't interchangeable.

• Use SHA-2 (SHA-256, SHA-512)for almost everything — TLS certificates, Bitcoin, Git, file integrity, package signing. It's ubiquitous, hardware-accelerated on most CPUs, and the default in nearly every standards body.
• Use SHA-3 / Keccakonly when a specific standard says so (Ethereum signing uses Keccak-256, some new government / financial regulations now require SHA-3, NIST's post-quantum signature schemes use SHA-3 internally).

Don't use raw hashes to store passwords

SHA-256(password) is dangerous — modern GPUs can compute billions of SHA-256 hashes per second, so any stolen password database is brute-force-able. Use a password hashing function instead:

• Argon2id — current OWASP recommendation, memory-hard
• bcrypt — battle-tested, work-factor tunable
• scrypt — memory-hard, predates Argon2
• PBKDF2 — FIPS-approved, often required for compliance

This calculator doesn't implement those by design — running them in JavaScript with conservative work factors would block the UI. Use a server-side library (bcryptjs, argon2-browser, etc.) for password hashing.

Standards & references

• FIPS 180-4 — Secure Hash Standard (SHA-1, SHA-2 family)
• FIPS 202 — SHA-3 family and SHAKE
• RFC 1321 — The MD5 Message-Digest Algorithm
• RFC 2104 — HMAC: Keyed-Hashing for Message Authentication
• RFC 4648 — Base16, Base32, Base64 encodings (used for hash output encoding)
• RFC 6234 — US Secure Hash Algorithms (SHA-2 reference implementation)
• IEEE 802.3 — CRC32 polynomial used by ZIP, PNG, gzip