Password Strength Checker
Entropy & brute-force resistance estimate for any password
For breach checking, only the first 5 characters of your password's SHA-1 hash are sent to the Have I Been Pwned API (k-anonymity model) — your full password never leaves the device. For maximum safety, test similar patterns rather than your exact password.
100% Private & In-Browser
Processed locally using client-side JavaScript. Your files and data never touch any server.
Instant & Unlimited
No registration, no waiting queues, and no limits on file conversions or generations.
What is Password Strength Checker?
The Password Strength Checker scores how resistant a password is to cracking — using entropy math rather than outdated 'complexity rules' — and explains exactly which choices made it weak or strong. It can optionally check the password against known breach databases using a zero-knowledge protocol that never sends the password itself.
How to use Password Strength Checker
Type the password into the field — everything is evaluated locally as you type.
The tool estimates entropy from length and character-space, then converts it into a realistic crack-time estimate.
Specific weaknesses (repeated patterns, dictionary words, short length) are flagged with concrete fixes.
Optionally run a k-anonymity breach check — only the first 5 hash characters leave your device.
- Entropy-based scoring aligned with modern NIST guidance
- Realistic crack-time estimates across online and offline attack scenarios
- Optional Have I Been Pwned check via zero-knowledge k-anonymity
- 100% local evaluation — the password itself never leaves your browser
- Auditing the passwords you actually use before they end up in a breach dump.
- Teaching why 'P@ssw0rd!' fails and long passphrases win.
- Validating password-policy implementations during development.
Frequently Asked Questions
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