Password Strength Checker
Test how secure your password is in real time. This tool uses the zxcvbn algorithm (developed by Dropbox) to estimate crack time, detect patterns, and provide actionable improvement suggestions. 100% browser-based — we never see your password.
The strength analysis runs entirely in your browser. Your password is NEVER transmitted to any server. We physically cannot see, log, or store what you type here.
Key Facts
- Algorithm: Uses zxcvbn by Dropbox — models real attacker strategies, not just character counting
- Analysis: Detects dictionary words, keyboard patterns, dates, sequences, l33t substitutions, and repeated characters
- Scoring: 5-level scale from Very Weak (0) to Very Strong (4) with estimated crack times
- Privacy: Zero server transmission — analysis runs locally in your browser via JavaScript
- Cost: 100% free, no registration, no limits
Password Strength Score Guide
- Score 0 — Very Weak: Crackable in seconds. Common passwords like "password" or "123456". Change immediately
- Score 1 — Weak: Crackable in minutes to hours. Short passwords or simple dictionary words. Not safe for any account
- Score 2 — Fair: Crackable in days to months. Reasonable for non-critical accounts but should be improved
- Score 3 — Strong: Crackable in years. Good for general accounts. Add length or complexity for sensitive accounts
- Score 4 — Very Strong: Crackable in centuries or more. Safe for banking, email, and critical accounts
How zxcvbn Strength Analysis Works
- Pattern Matching: Unlike simple meters that only check length and character types, zxcvbn identifies real patterns attackers exploit: dictionary words, names, dates, keyboard sequences (qwerty, zxcvbn), and l33t speak substitutions
- Crack Time Estimation: Provides realistic estimates for multiple attack scenarios including offline slow hashing (10,000 guesses/sec) and online throttled attacks (10 guesses/sec)
- Actionable Feedback: Gives specific suggestions like "Add a word or two" or "Avoid sequences" instead of generic "use symbols" advice
- Library Size: ~400KB loaded on demand — includes dictionaries of common passwords, English words, names, and known patterns
Frequently Asked Questions
How does the password strength checker work?
It uses the zxcvbn algorithm developed by Dropbox, which estimates crack time by detecting patterns like dictionary words, keyboard sequences, dates, and common substitutions. Unlike simple checkers that only count character types, zxcvbn models the strategies real attackers use.
Can you see the password I type?
No. The analysis runs entirely in your browser using JavaScript. Your password is never transmitted to any server. You can verify by monitoring the Network tab in your browser developer tools while testing passwords.
What is a good password strength score?
Aim for a score of 4 (Very Strong), meaning your password would take centuries to crack. Score 3 (Strong) is acceptable for non-critical accounts. Scores of 0 through 2 indicate significant vulnerability and those passwords should be changed immediately.
Why does my long password still get a low score?
Length alone does not guarantee strength. A password like "aaaaaaaaaaaaaaaa" is long but trivially crackable. zxcvbn detects repeated characters, dictionary words, and predictable patterns regardless of length. A truly strong password combines length with randomness.
How can I improve my password strength?
Increase length to at least 16 characters. Avoid dictionary words, names, dates, and keyboard patterns. Use a random password generator (like our Password Generator) instead of creating passwords from memory. Store strong passwords in a password manager.
Password Security Statistics
- 81% of data breaches involve weak or stolen passwords (Verizon 2024 DBIR)
- 59% of people reuse passwords across multiple sites (Google/Harris Poll 2024)
- 8-character passwords with only lowercase letters can be cracked in approximately 2 hours
- 16-character mixed passwords with all character types would take approximately 34,000 years to brute-force
- Top 3 most common passwords remain "123456", "password", and "123456789" (NordPass 2024)