Password Strength Checker
Test how strong your password is. Get entropy analysis, crack time estimates, and actionable tips to improve your security. 100% client-side — nothing leaves your browser.
Why Password Strength Matters
Weak passwords are the #1 cause of data breaches. Over 80% of hacking-related breaches involve stolen or weak credentials. A password that seems “good enough” to a human can often be cracked in seconds by modern hardware running billions of guesses per second. Password strength isn't just about mixing characters — it's about entropy, unpredictability, and avoiding patterns that attackers already know.
How We Calculate Password Strength
Character Pool & Entropy
We calculate Shannon entropy based on the character types used (lowercase, uppercase, numbers, symbols) and password length. Higher entropy means exponentially more guesses required to crack.
Pattern Detection
We check for keyboard patterns (qwerty, asdf), sequential characters (abc, 123), and repeated characters (aaa). These patterns dramatically reduce effective entropy even in long passwords.
Common Password Lists
We compare against known commonly-used passwords. If your password appears on these lists, attackers will try it first — making length and complexity irrelevant.
Crack Time Estimation
We estimate how long a brute-force attack would take at 10 billion guesses per second — representative of a modern GPU cluster. Real attacks may use optimized wordlists and be faster.
Frequently Asked Questions
Is it safe to type my real password here?
Yes. This tool runs entirely in your browser using JavaScript. Your password is never sent to any server, stored, or logged. You can verify this by checking your browser's network tab — no requests are made when you type.
What makes a strong password?
A strong password has high entropy — meaning it's long, uses a mix of character types (uppercase, lowercase, numbers, symbols), and avoids predictable patterns. A 16+ character random passphrase is generally stronger than a short complex password like 'P@ss1'.
How long should my password be?
At minimum 12 characters, ideally 16+. Each additional character exponentially increases the number of guesses needed. A 20-character passphrase made of random words is both strong and memorable.
Should I use a password manager?
Absolutely. Password managers generate unique, strong passwords for every account and store them securely. This eliminates the biggest risk: reusing passwords across sites. If one site is breached, only that password is compromised.
How accurate is the crack time estimate?
It's a rough estimate based on brute-force at 10 billion guesses/second (modern GPU cluster). Real attacks often use dictionaries, rules, and patterns that can be faster for predictable passwords. For truly random passwords, the estimate is conservative.