· Cybersecurity tool · Strength + breach exposure · 100% client-side

Cybersecurity password health checker

Two checks in one place. Strength is computed in your browser using a rule-based entropy approximation calibrated to NIST SP 800-63B Appendix A bands. Breach exposure is checked against Have I Been Pwned using the k-anonymity model: only the first 5 hex characters of the SHA-1 hash are sent to HIBP, never the password itself or the full hash.

Type a password to test

Strength is computed in your browser. The breach check sends only the first 5 characters of the SHA-1 hash to HIBP (k-anonymity model); the password itself never leaves your device.

What does the strength score actually measure?

The score approximates Shannon entropy of the password against a charset estimate (lowercase, uppercase, digits, symbols), then penalizes common patterns (sequences, repeats, dictionary words like "password" or "qwerty"). The bands map roughly to NIST SP 800-63B Appendix A guidance: under 30 bits of effective entropy is "very weak," 50-70 is "fair," 70+ is "good," 90+ is "strong." For audit-grade analysis, run the password through the full zxcvbn library or a corporate password manager's strength meter.

Why these two checks together

A password can be high-entropy and still be in attacker word lists if a user has reused it from a breached site. The strength bar tells you whether the password is hard to guess from scratch. The HIBP check tells you whether the password is already in a credential-stuffing corpus. Both can fail independently. Both should pass before you trust a password on any account that matters.

For organizational use, NIST SP 800-63B recommends checking new passwords against breach corpora at the point of registration. The Have I Been Pwned API is the most widely-adopted public source for this; many IDPs (Okta, Azure AD, Auth0) integrate it by default.

Sources

Last verified: April 2026?Report an inaccuracy

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