Password Strength Checker — Free Online Tool
Check the strength of any password using Dropbox's zxcvbn algorithm, which matches against real-world patterns, common words, keyboard patterns, and leaked passwords — not just checking if you have uppercase and a number. Shows crack time estimate (offline fast attack), weakness warnings, and specific improvement suggestions.
100% client-side. No uploads. Your data never leaves your browser.
How to use Password Strength Checker
- Type a password into the input field.
- The strength score (0–4), crack time estimate, and specific warnings appear instantly.
- Read the 'Suggestions' section for targeted improvements.
- The password input never persists — it is cleared when you navigate away.
Frequently Asked Questions
Is my password sent anywhere?
No. This is 100% client-side. The zxcvbn library runs entirely in your browser and your password never leaves your tab.
Why is a long password with no symbols weak?
zxcvbn checks for patterns. 'password123' scores 0 because it matches common password databases. A random mix of words (passphrase) often scores higher than short symbol-heavy passwords.
What does 'crack time' mean?
The estimated time to crack the password in an offline attack using optimized hardware running billions of guesses per second.
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