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. All analysis runs locally in your browser.

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.

Use Cases

The Password Strength Checker is used to verify new passwords meet best practices, compare strong and weak passwords during IT training, and help developers understand how entropy and rules interact.

FAQ

• What is entropy? — Entropy measures the unpredictability of a password in bits. It is calculated as log₂(pool size) × length. A score of 60+ bits is generally considered strong.
• Is my password sent anywhere? — No. All analysis runs in JavaScript in your browser. Your password never leaves your device.
• Why does a long lowercase-only password score lower than a short mixed one? — Length and character variety both matter. Lowercase-only has a pool of 26 characters, while mixed uses 94. The score balances both factors.