Password Strength Checker

About This Tool

The Password Strength Checker analyzes a password in real time against eight security rules: length thresholds, character class variety (uppercase, lowercase, digits, symbols), absence of repeated characters, and absence of common keyboard sequences. It also calculates the theoretical entropy — the number of bits of randomness — based on the character pool size and password length.

Higher entropy means more guesses an attacker needs to brute-force the password. A score of 60+ bits is generally considered strong for most purposes. All analysis runs locally in your browser — your password is never sent to any server.

How to Use

1. Type or paste a password into the input field.
2. The strength bar, label, and checks update instantly as you type.
3. Review the Checks list to see which criteria pass or fail.
4. Follow the Suggestions to improve the password.
5. Toggle Show/Hide to verify what you typed.

Use Cases

Security-conscious users verify that a new password meets best-practice requirements before setting it. IT administrators use the tool to demonstrate password policy requirements during onboarding. Developers integrate the same heuristics into their own password validation logic after seeing how entropy and rules interact. Students learning about authentication compare strong and weak passwords to build intuition about what makes a password difficult to crack.

FAQ

• Is my password sent anywhere? — No. All analysis runs in JavaScript in your browser. Your password never leaves your device.
• What is entropy? — Entropy measures the unpredictability of a password in bits. It is calculated as log₂(pool size) × length. A pool of 94 characters with 12 characters gives ≈78 bits, which is very strong.
• Why does a 16-character lowercase-only password score lower than a short mixed password? — Length and character variety both matter. A 16-character lowercase string has a smaller pool (26 chars) than a mixed 8-character string (94 chars), but the total entropy may still be higher due to length. The score balances both.
• Does this check against data breach databases? — No. For breach checking, use a service like HaveIBeenPwned. This tool focuses on rule-based and entropy-based analysis only.