Password Strength Checker
Estimate password strength with entropy calculation, character-class scoring, common-password detection, pattern analysis, and 10+ extras. 100% private.
About Password Strength Checker
Estimate password strength with entropy calculation, character-class scoring, common-password detection, pattern analysis, and 10+ extras. 100% private. Everything runs locally in your browser — your data never leaves your device.
How to use
- Enter your input in the tool above.
- Adjust any options to your preference.
- Use the Copy or Download buttons to save the result.
- Everything happens locally — your data never leaves your browser.
FAQ
How is password strength calculated?
We compute Shannon entropy (log2 of pool size × length), detect common patterns (sequential digits, repeated chars, keyboard walks like 'qwerty'), check against a list of the 10,000 most common passwords, and apply NIST SP 800-63B bonus/penalty rules.
What extras does this tool have?
Extras: (1) Shannon entropy in bits, (2) Character pool size + class breakdown, (3) Crack-time estimate (offline fast hashing), (4) Common password detection (10k list), (5) Pattern detection (sequential/repeated/keyboard), (6) Dictionary word detection, (7) Leet-speak normalization, (8) 0-4 strength score, (9) Per-character analysis, (10) Suggestions for improvement, (11) Batch mode (check multiple passwords), (12) CSV export of batch, (13) Show/hide password toggle, (14) Compare two passwords side-by-side.
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