Password Strength Checker
Check password strength with entropy calculation, pattern detection and common password matching.
How to Use the Password Strength Checker
Type or paste a password into the input field. The tool instantly analyzes its strength based on length, character variety, common patterns, and entropy. A color-coded strength bar shows the result: Very Weak, Weak, Fair, Strong, or Very Strong.
What Makes a Strong Password?
- Length — 16+ characters significantly increases security
- Character variety — mix of uppercase, lowercase, numbers, and symbols
- No common patterns — avoid dictionary words, sequential characters, and repeated characters
- Uniqueness — never reuse passwords across accounts
How Strength is Calculated
The checker evaluates password length, character diversity (uppercase, lowercase, digits, symbols), detects common passwords, repeated characters, and sequential patterns. It also calculates Shannon entropy — the mathematical measure of password randomness.
Frequently Asked Questions
Is my password sent to a server?
No. All analysis happens entirely in your browser. Your password never leaves your device — there are no network requests made by this tool.
How accurate is this strength checker?
It checks for length, character variety, common password lists, repeated characters, and sequential patterns. While no client-side checker can detect every weak pattern, it covers the most important factors that determine password security.
What entropy is considered safe?
Passwords with 60+ bits of entropy are considered strong. 80+ bits is very strong. For reference, a random 16-character password using all character types has about 105 bits of entropy.
Does it check against breach databases?
No. This tool runs entirely offline in your browser. For breach database checks, use a service like Have I Been Pwned. This checker focuses on structural analysis and pattern detection.
Why is my long password rated as weak?
A long password can still be weak if it uses only one character type (e.g., all lowercase), contains common words, or has repeated/sequential patterns. A strong password needs both length and complexity.
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