A hash turns any text into a fixed-length fingerprint. This SHA-1 hash calculator gives you the 160-bit SHA-1 fingerprint of anything you type — instantly, and entirely inside your browser. Developers use it to compare file versions, check Git object IDs and spot when two pieces of text are not identical.
Type or paste into the box and the hash updates as you type. Nothing is sent to a server, so it is safe to test with private strings you would never paste into a random web form.
What SHA-1 is, in plain words
SHA-1 (Secure Hash Algorithm 1) was published by the NSA in 1995. It reads input of any length — a word, a sentence, a whole file — and produces a 160-bit result, always written as 40 hexadecimal characters. The operation only goes one way: you cannot run the hash backwards to recover the original text. Change a single character in the input, even just its capitalisation, and roughly half of the output characters change. That sensitivity is exactly what makes hashes useful as fingerprints.
A worked example
Type the sentence The quick brown fox jumps over the lazy dog into the calculator and you get 2fd4e1c67a2d28fced849ee1bb76e7391b93eb12. That value is the published reference result for this sentence, so it doubles as a self-test: if your output matches, the tool is working correctly. Now change the final full-stop or make the first letter lower-case and watch the whole fingerprint change.
Where SHA-1 is still used
Git. Every commit, tree and blob in Git is identified by a SHA-1 hash, so you will meet these 40-character strings daily if you work with code. Checksums. Older download pages and internal tools still publish SHA-1 sums for verifying that a file arrived intact. Legacy systems. Older TLS certificates, document-signing tools and content-addressed caches were built on SHA-1 and still surface in maintenance work. In all of these roles SHA-1 is used as an identifier or a tamper-evident label, not as a security wall.
The honest warning: SHA-1 is broken for security
In 2017 researchers produced two different PDF files with the same SHA-1 hash (the “SHAttered” attack), proving that collisions can be manufactured on purpose. That kills SHA-1 for anything adversarial: do not use it for password storage, digital signatures, certificate fingerprints or proving a file has not been maliciously altered. Modern browsers and operating systems reject SHA-1 certificates for this reason. For integrity checks against accidents — a corrupted download, a truncated copy-paste — it still works fine, but where an attacker is part of the picture, use SHA-256 or SHA-512 instead. And never hash passwords with any fast hash, SHA-1 included; passwords belong in bcrypt or Argon2.
How to use this calculator
There is nothing to configure. Type or paste your text and read the hash. The character counter under the box shows the input length and confirms the output is always 40 hex characters. Use the copy button to grab the hash without risking a missed character — a single wrong digit makes a hash useless for comparison.
Frequently asked questions
Can a SHA-1 hash be reversed or decrypted?
No. SHA-1 is a one-way function, not encryption; there is no key and no reverse operation. Short inputs can be guessed by trying likely candidates (which is why unsalted hashes of weak passwords fall quickly), but the hash itself cannot be inverted.
Why does the hash of empty text still exist?
Because a hash is defined for every input, including nothing at all. The SHA-1 of the empty string is da39a3ee5e6b4b0d3255bfef95601890afd80709 — clear the box and you will see exactly that.
What is the difference between SHA-1 and SHA-256?
Length and strength. SHA-256 produces 256 bits (64 hex characters) and has no known practical collision attack; SHA-1 produces 160 bits and does. For new projects, prefer the SHA-2 family.
Is my text uploaded anywhere?
No. The calculation uses the WebCrypto API built into your browser. You can disconnect from the internet after the page loads and the calculator keeps working.
Related tools
Versión en español: Calculadora de Hash SHA-1 — Genera Hashes SHA-1 de Texto Gratis y Online. You may also like: SHA-512 Hash Calculator — Free Online SHA-512 Generator for Text · Bcrypt Hash Generator and Checker — Hash and Verify Passwords Online.
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