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🔐 Password Strength Checker — Local Heuristic

Type a password to see a length-and-variety score, an estimated entropy figure, and which character classes are missing. Nothing leaves the page.

Security Free · no sign-up Added 2026-10-08
Input
Result
Summary

Private by design. This tool runs entirely in your browser — nothing you enter or add is uploaded to any server.

How it works

  1. Type a password. It is read only from this page.
  2. Press Score. The heuristic counts length and whether lowercase, uppercase, digits and symbols appear.
  3. Read the band and the missing classes. This is not a breach-database check.

Examples

  • password scores weak because it is short and one class.
  • Correct-horse-battery scores higher on length even without digits.
  • A 16-character mix of classes reaches the strong band.

Frequently asked questions

Is the password sent anywhere?

No. Scoring uses the characters in the field and does not call a server or a breach API.

Does a high score mean the password is safe?

No. The score is a local length-and-variety heuristic. Reused or previously leaked passwords can still be unsafe.

How is entropy estimated?

Each character class adds a pool size (26, 26, 10 or 33). Entropy is length times log2 of the pool. It assumes random characters, which real phrases are not.

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