Password Strength Checker
Test your password strength with entropy analysis, crack time estimates, and actionable security suggestions.
How to Use the Password Strength Checker
- Type or paste your password into the input field.
- The tool instantly analyzes entropy, character diversity, length, and common patterns.
- Review the strength score, estimated crack time, and detailed breakdown.
- Follow the suggested improvements to make your password stronger.
How Password Strength is Measured
Password strength is typically measured in bits of entropy, which represents the number of guesses an attacker would need to try in a brute-force attack. A password with 40 bits of entropy has 2^40 (about 1 trillion) possible combinations. However, raw entropy based on character count alone does not tell the full story, because real attackers do not use pure brute force. Modern password cracking employs dictionary attacks, rule-based mutations, Markov chains, and leaked password databases. A password like 'P@ssw0rd123' may look strong by simple metrics but is trivially cracked because it follows common substitution patterns found in nearly every password wordlist. Effective strength analysis must detect these patterns: dictionary words, keyboard walks (qwerty), repeated characters, dates, l33t speak substitutions, and sequences. This tool performs analysis entirely in your browser. Your password is never transmitted to any server. It evaluates entropy based on the character space used, detects common patterns and dictionary words, estimates crack time against various attack scenarios (online throttled, offline slow hash, offline fast hash), and provides specific recommendations for improvement. Remember that even a strong password should be unique per account and paired with two-factor authentication.
Frequently Asked Questions
No. This tool runs entirely in your browser. Your password never leaves your device. All analysis including pattern detection, entropy calculation, and crack time estimation is performed client-side using JavaScript. You can verify this by monitoring your browser's network activity.
Entropy measures the unpredictability of a password in bits. Higher entropy means more possible combinations an attacker must try. A password with 80 bits of entropy would take billions of years to brute-force with current hardware. However, entropy alone does not account for pattern-based attacks, which is why this tool also checks for common patterns.
Special characters alone do not make a password strong. If the underlying word is common (like 'Password!') or follows predictable substitution patterns (like 'P@$$w0rd'), attackers will crack it quickly using rule-based attacks. True strength comes from length, randomness, and avoiding patterns found in leaked password databases.