Password Strength Checker

Test how strong your password is — entropy, crack time, and improvement tips.

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Entropy
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Estimated crack time
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Length
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Character set size
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How Password Strength is Calculated

This checker measures password strength using entropy — a mathematical measure of unpredictability. Entropy is calculated as: log₂(charset size ^ length). The character set size depends on which types of characters you use: lowercase letters (26), uppercase (26), numbers (10), and symbols (~32). A password using all four types and 12+ characters typically has 70+ bits of entropy, which is considered strong.

The crack time estimate assumes an attacker can try 10 billion passwords per second (representing a powerful GPU cracking rig). This is deliberately conservative — real attackers may be faster or slower. Your password is never sent anywhere — all analysis happens entirely in your browser using JavaScript. The page does not log, store, or transmit anything you type.

How to Use

  1. Type or paste your password into the field above.
  2. The strength meter, entropy score and crack time estimate update instantly.
  3. Check the requirements list to see what your password is missing.
  4. Follow the improvement suggestions to make it stronger.
  5. Click the 👁 button to show or hide the password characters.

Frequently Asked Questions

Yes. This tool runs entirely in your browser with no server communication. Your password is never sent anywhere, logged, or stored. You can verify this by disconnecting from the internet before using it — the tool works offline. That said, as a general security practice it is wise to be thoughtful about where you type passwords. You can also test a similar but not identical password to get a representative score.

Security experts recommend at least 12–16 characters for regular accounts and 20+ for high-value accounts. Length is the single most effective way to increase entropy. A 20-character password of lowercase letters only (26^20 combinations) is stronger than an 8-character password using all character types. A passphrase of 4–5 random words is often more memorable than a complex 12-character password and equally strong.

No. This tool runs entirely in your browser. Your password is never sent to any server, never logged, and never stored. Closing the tab removes all data immediately.
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