Bcrypt Hash Generator & Comparator

Generate a bcrypt hash with an adjustable round (cost) count for a password, or compare a piece of text against an existing bcrypt hash to see whether it matches.

Runs 100% in your browser — the text and hash you enter are never sent to a server.

Generate Bcrypt Hash

Recommended: 10-12. Every extra round doubles the computation time — higher rounds are more secure but slower.

Compare Hash

What Is Bcrypt, and Why Is It Used for Password Storage?

Bcrypt is a hash function designed specifically for storing passwords. Unlike general-purpose hash functions such as MD5 or SHA-256, bcrypt is deliberately slow, and that slowness can be tuned with a "round" (cost factor) parameter — as the round count increases, the computation time grows exponentially (by a factor of 2^rounds). This design aims to make brute-force attacks, where an attacker tries millions of candidate passwords within seconds, practically infeasible.

Salt is included automatically: bcrypt automatically adds a random "salt" to every hash and embeds it inside the generated hash string itself (in the form $2a$10$saltAndHashValue…). This means the same password produces a different hash every time, which renders precomputed "rainbow table" attacks useless — and you don't need to store the salt separately for comparison either, the compare function extracts it from the hash itself.

This tool hashes or compares the text you enter entirely in your browser using the bcryptjs library — no data is ever sent to a server. In a real application, password hashing should be performed server-side; this tool is intended only for testing, learning, and quick verification.

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Frequently Asked Questions

Bcrypt is a hash function introduced in 1999, designed specifically for password storage. It's based on a variant of the Blowfish encryption algorithm and is deliberately designed to be slow — this slowness makes brute-force attacks expensive and practically infeasible. The hash it produces looks like $2a$10$…: it packs the algorithm version, the round count, the salt, and the actual digest into a single string.

The round count determines how many times (2rounds times) bcrypt repeats its internal mixing operation. Increasing rounds by 1 roughly doubles the computation time — the difference between round 10 and round 12 is a factor of four. The default of 10 used in this tool strikes a good balance between security and performance on today's hardware; more sensitive systems may prefer 12-14, but every increase slows down both hashing and comparison.

General-purpose hash functions like MD5 and SHA-256 can be computed billions of times per second — that's an advantage for file integrity checks, but the opposite is true for password storage, since an attacker can try a huge number of candidate passwords against a stolen hash database in a very short time. Bcrypt, by contrast, is deliberately slow and carries an adjustable cost (rounds) parameter, so the same attack becomes far more expensive and slower against bcrypt. Bcrypt also automatically adds a unique salt to every hash, which makes precomputed "rainbow table" attacks useless.

No. Bcrypt is a one-way function — it's not encryption, so there's no mathematical way to go back from the hash to the original text. To check whether a password is correct, the hash isn't "decrypted"; instead the entered text is re-hashed with the same salt and round count, and the result is compared against the stored hash (this is exactly what the "Compare" section of this tool does). The only practical way to find a password from a hash is to try every possible password and compare its hash — bcrypt's deliberate slowness makes this method costly enough too.

No. Both hashing and comparison happen entirely in your browser, in your device's memory, using the bcryptjs library loaded on the page. The text and hash you enter are never included in any network request and are never written to localStorage; everything is lost when you refresh the page.

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