Bcrypt Generator & Verifier

Hash passwords with bcrypt and verify passwords against existing hashes. Processing done server-side with PHP's password_hash().

Password
Cost Factor: 12
Higher cost = slower hashing = harder to brute-force. Cost 12 is the recommended default.

Frequently Asked Questions

Bcrypt is intentionally slow, making brute-force and dictionary attacks extremely expensive. It includes a random 128-bit salt automatically, so identical passwords produce different hashes. The cost factor lets you increase work as hardware gets faster. This is why every major security framework recommends bcrypt (or Argon2) over MD5, SHA-1, or other fast hashes for passwords.
The cost factor (also called the "work factor") is the log₂ of the number of iterations. Cost 12 = 2¹² = 4,096 rounds. Each increment doubles the computation time. OWASP recommends a minimum cost of 10, and at least 12 for new applications. Tune it so hashing takes ~250ms–1s on your production server.
Argon2id is the current OWASP and NIST recommendation for new systems — it won the 2015 Password Hashing Competition and is resistant to both GPU and side-channel attacks. scrypt is memory-hard, making it resistant to GPU brute-force. bcrypt is CPU-intensive but not memory-hard. If you're building a new system, prefer Argon2id. If your system already uses bcrypt with a good cost factor, it remains secure.
Bcrypt is a one-way hash — it cannot be decrypted. Verification works by re-hashing the input password using the same salt embedded in the stored hash, then comparing the results. The salt is embedded in the hash string (the 22 characters after the cost factor). In PHP: password_verify($password, $hash) does this automatically. Never compare bcrypt hashes with === — always use the library's built-in constant-time verify function to prevent timing attacks.
Yes. Bcrypt truncates input at 72 bytes — any characters beyond that are silently ignored. For most passwords this is not a practical issue, but for extremely long passphrases it matters. Mitigation: pre-hash the password with SHA-256 (as raw binary, not hex) before passing to bcrypt — this gives you effectively unlimited password length while keeping bcrypt's salting and slowness. Some frameworks (like Laravel 10) implement this pre-hashing automatically.
Encryption is reversible — if the decryption key is ever leaked, all stored passwords are immediately exposed. Hashing is one-way — there is no key to leak. Even if your entire database is stolen, an attacker must brute-force each hash individually. Passwords should never need to be decrypted — the correct model is: user provides password → server re-hashes it → compare to stored hash.
A timing attack exploits the fact that string comparison functions (===, strcmp) return early as soon as they find a mismatch — the comparison takes measurably less time for incorrect values that differ at the first character. By measuring thousands of response times, an attacker can statistically determine correct bytes one by one. PHP's password_verify() and hash_equals() use constant-time comparison — never use === to compare hashes or tokens.
To hash: $hash = password_hash($password, PASSWORD_BCRYPT, ['cost' => 12]); — store the resulting 60-character string in your database. To verify: if (password_verify($input, $storedHash)) { /* authenticated */ }. To check if rehashing is needed: if (password_needs_rehash($hash, PASSWORD_BCRYPT, ['cost' => 12])) { $hash = password_hash($password, PASSWORD_BCRYPT, ['cost' => 12]); }.
A pepper is a secret value stored in application config (not the database) that is HMAC'd with the password before hashing. If the database is stolen but the application server is not, the attacker cannot crack the hashes without the pepper. Implementation: $peppered = hash_hmac('sha256', $password, $PEPPER); $hash = password_hash($peppered, PASSWORD_BCRYPT);. OWASP considers peppers a reasonable additional control for high-security applications.
$2a$ is the original bcrypt format with a bug in some implementations regarding 8-bit characters. $2b$ is the corrected format (fixed in OpenBSD). $2y$ is PHP-specific and equivalent to $2b$ — introduced before the official fix to signal the corrected behavior. For new hashes PHP uses $2y$. All three verify correctly against each other in modern implementations.

About This Bcrypt Generator

This free bcrypt generator hashes a password using the bcrypt algorithm with a configurable cost factor. Enter a password and select a cost to generate a hash suitable for storing in a database.

When to use this tool

  • Generating test bcrypt hashes during development
  • Verifying that your application stores passwords correctly
  • Understanding how cost factor affects computation time
  • Creating hashes for seeding a user database

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