Password Checker
Analyze password strength instantly. Get entropy, crack time estimates, pass/fail criteria, and actionable improvement tips — all in your browser.
- Length—
- Charset size—
- Entropy—
- Online attack—
- Offline attack—
Need to create a strong password? Try our Password Generator.
Password Checker analyzes your password in real time — right in your browser. No data is sent to any server.
Features
| Feature | Details |
|---|---|
| Strength meter | 5 levels: Very Weak / Weak / Fair / Strong / Very Strong |
| Entropy analysis | Calculates bits of entropy based on character variety and length |
| Crack time estimate | Online (1k/sec) and offline GPU (10B/sec) scenarios |
| 11 criteria checks | Length, uppercase, lowercase, numbers, symbols, repeats, sequences, common passwords |
| Suggestions | Actionable tips to improve weak passwords |
| Show / hide toggle | Reveal or mask the password at any time |
| Copy button | One-click copy to clipboard |
| 100% client-side | Nothing leaves your browser |
How to Use
- Type or paste your password into the input field.
- The strength meter and criteria checklist update instantly.
- Read the Statistics panel for entropy and estimated crack times.
- Follow the Suggestions box to fix weaknesses.
- Need a new strong password? Use our Password Generator.
Understanding the Results
Entropy measures unpredictability in bits. The higher the number, the harder the password is to crack by brute force.
| Entropy | Strength |
|---|---|
| < 28 bits | Very Weak |
| 28–35 bits | Weak |
| 36–59 bits | Fair |
| 60–127 bits | Strong |
| 128+ bits | Very Strong |
Crack time assumes an attacker tries every possible combination:
- Online attack — 1,000 guesses/sec (rate-limited web login)
- Offline attack — 10 billion guesses/sec (modern GPU hash cracking)
Frequently Asked Questions
Is my password sent to your server?
No. All analysis runs entirely in your browser using JavaScript. Your password never leaves your device.
Why does a short password with symbols still score low?
Length has a far greater impact on entropy than character variety alone. A 6-character password with symbols is still much weaker than a 16-character lowercase-only password.
What makes a password "common"?
The tool checks your password against a built-in list of the most frequently used passwords (e.g. "password", "123456", "qwerty"). If your password matches, the score is capped at Very Weak regardless of other factors.
How is entropy calculated?
Entropy = length × log₂(charset size). The charset size is the number of distinct character categories present: lowercase (26), uppercase (26), digits (10), symbols (32).
What length should I aim for?
For general accounts aim for at least 12 characters; for high-value accounts (email, banking) use 16 or more. A password manager makes this easy.
What are sequential patterns?
Runs like "123", "456", "abc", "xyz" are detected and flagged. Attackers include these patterns in their dictionaries.
What is a passphrase?
A passphrase is multiple random words joined together, e.g. "correct-horse-battery-staple". It can achieve high entropy with fewer characters and is easier to remember.
How can I create a strong password?
Use our Password Generator to instantly create a secure, random password of any length.