100% Client-Side

Password Strength Checker

Real-time password analysis with entropy, crack time, and improvement tips

Free Client-Side No Login No Storage
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Random Password Generator Generate strong, cryptographically secure passwords — customizable length and charset Bcrypt Hash Generator Hash passwords with bcrypt — configure cost factor, verify hashes HMAC Generator Generate HMAC message authentication codes — SHA256, SHA512, SHA1, MD5

How to Use the Password Strength Checker

  1. Type or paste a password into the field.
  2. Strength score, entropy (bits), and estimated crack time are shown instantly.
  3. Follow the suggestions to improve weak passwords.

What makes a strong password?

  • Length — 16+ characters is significantly stronger than 8
  • Character variety — mix uppercase, lowercase, numbers, and symbols
  • Unpredictability — avoid dictionary words, names, or keyboard patterns
  • Uniqueness — never reuse passwords across sites

Privacy note: Your password never leaves your browser. All analysis is done client-side with zero network requests.

What is Password Strength & Entropy Analysis?

The Password Strength Checker evaluates passwords against modern security benchmarks, calculating mathematical information entropy in bits, estimated brute-force crack times against GPU clusters, and checking for common patterns, dictionary words, and sequential characters. It provides actionable recommendations based on NIST SP 800-63B guidelines.

Common Uses

  • Auditing personal and organizational password resilience against dictionary attacks
  • Testing password complexity validation rules prior to deploying auth systems
  • Educating teams on the superior entropy of multi-word passphrases over short complex strings
  • Verifying credentials against common substitution patterns (e.g. `P@ssw0rd`)

Frequently Asked Questions

What is password entropy?

Password entropy is a mathematical measurement of password unpredictability expressed in bits. A password with 80 bits of entropy would take billions of guesses to crack, providing strong protection against offline brute-force attacks.

Why does NIST recommend long passphrases over complex short passwords?

NIST SP 800-63B highlights that password length is far more effective at resisting modern cracking hardware than arbitrary complexity rules. A four-word passphrase like `correct-horse-battery-staple` is easy for humans to remember but computationally infeasible to brute-force.

Is my password sent to a server when I test it?

Never. The entropy analysis algorithm runs entirely client-side in your browser via local JavaScript. No keystrokes or password strings are ever sent over the network.

Notes from this implementation

A guess about guessing, not a breach check

The meter estimates how large the search space is from the character classes you actually used, and it penalizes repeats and sequences. It does not query Have I Been Pwned, and it does not know whether this password is already in a dump. “Strong” on this page can still be a password you reused on a site that was breached.

Length beats decoration. correct horse battery staple style passphrases score well because of length. P@ssw0rd! scores worse than the character classes suggest, because it is a template. The meter is a teaching tool. Your account policy should set a minimum length and check against breached-password lists on the server.

What not to paste

The value stays in the browser script, but the machine, the extensions, and a shoulder are still there. Type a similar example, not the password for your bank.