Hash a password with bcrypt at cost 4–15, verify a password against a $2a$/$2b$/$2y$ hash, and inspect a hash's version, cost and salt. Runs in a worker; nothing is stored.
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bcrypt is the password hash behind a large share of the web — Laravel, Rails' has_secure_password, Spring Security's BCryptPasswordEncoder, Django's optional hasher, and countless Node apps. When a login stops working after a migration, or you need a hash to seed a test user, you want to check a password against a hash without writing a script. This tool does three things. Generate hashes a password at a cost factor from 4 to 15 in a background Web Worker, showing how long it took and letting you cancel slow high-cost runs. Verify checks a password against any $2a$, $2b$ or $2y$ hash. Inspect splits a hash into its version, cost, salt and hash parts, with a specific error when a hash is truncated (a database column shorter than 60 characters is a classic cause), has the wrong prefix, or is actually a different algorithm such as SHA-512-crypt or Argon2. It warns when a password is longer than bcrypt's 72-byte limit. Output is tested against pyca/bcrypt on the OpenBSD test vectors.
$2b$10$ then 53 characters: 22 characters of salt (16 bytes in bcrypt's own Base64 alphabet, ./A–Za–z0–9) and 31 characters of hash (23 bytes). The cost is log2 of the number of key-setup rounds: 10 means 1,024 rounds.
Hashing uses bcryptjs, a pure-JavaScript bcrypt, running in a Web Worker so the page stays responsive. Verification uses a constant-time comparison. $2y$ and $2b$ hashes are handled as the same algorithm; generated hashes use $2b$.
The password is kept only in the page's memory while you use it. It is not saved in local storage, not included in any link, and not sent to analytics.
The unit tests reproduce the classic OpenBSD / jBCrypt vectors and additional cases (Unicode, the 72-byte boundary, $2y$) generated with pyca/bcrypt, an independent implementation, and round-trip random passwords.
Short answers for the things developers usually ask before trusting a tool.
No. Hashing and verification run in a Web Worker in your browser. Passwords and hashes are never stored, logged, or put in a share link. Even so, this tool is for testing and learning — in production, hash passwords on your server with your framework's password hasher.
Pick the highest cost your server can afford per login — commonly 10–12 today, aiming for roughly 100–300 ms per hash on your hardware. Each +1 doubles the time. OWASP currently recommends at least 10. Browsers are slower than servers, so costs of 13+ can take several seconds here; you can cancel.
They are the same algorithm with different histories. $2a$ is the long-standing format; $2b$ was introduced by OpenBSD in 2014 to fix a bug with passwords longer than 255 bytes; $2y$ is PHP's marker for its fixed implementation. For normal passwords all three produce the same hash, and this tool verifies all of them. ($2x$ marks hashes from an old buggy PHP implementation and may not verify for non-ASCII passwords.)
bcrypt only uses the first 72 bytes of the password — bytes of UTF-8, not characters, so a password of 36 characters like "é" already reaches it. Anything after byte 72 is ignored. The tool warns when you go over. If you need longer inputs, pre-hash with SHA-256 (carefully, Base64-encoded to avoid NUL bytes) or use Argon2id.
Each hash includes a random 16-byte salt (the 22 characters after the cost). The salt is stored in the hash, so verification reads it back and recomputes. Two users with the same password get different hashes, which defeats precomputed rainbow tables.
Yes for most applications, and it's the default in many frameworks. Argon2id is the current OWASP first choice because it is also memory-hard, which slows GPU cracking more. If you already use bcrypt with a reasonable cost, there is no urgency to migrate.
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