Password Strength Checker

Check how strong a password is, with an entropy estimate and a checklist of specific criteria — length, character variety, and common-password patterns. Your password is never sent anywhere.

Password

This runs entirely in your browser — your password is never sent anywhere.

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Your feedback helps us improve Password Strength Checker.

Why use Password Strength Checker?

This tool evaluates password strength using a checklist of criteria — length, character variety, repeated-character runs, and common weak patterns — and estimates entropy in bits based on password length and character pool size. Everything runs locally in your browser; your password is never transmitted anywhere.

Key benefits

Entropy estimate in bits, not just a vague rating
Detailed pass/fail checklist for each criterion
Runs entirely in your browser — your password is never transmitted

Features

Length, character-variety, and repetition checks
Common-password pattern detection
Bits-of-entropy estimate

Popular use cases

Checking a new password before setting it on an account
Testing password policy requirements
Learning what makes a password strong

How to use Password Strength Checker

1
Type a password
Enter a password into the field — click Show to reveal it while typing.
2
Review the results
See the strength rating, entropy estimate, and which criteria are met.

Frequently asked questions

How is entropy calculated?

Entropy is estimated as password length × log2(character pool size), where the pool size depends on which character types (lowercase, uppercase, digits, symbols) are used.

Is my password sent to a server?

No. All analysis happens locally in your browser using JavaScript — your password is never transmitted or logged.

What counts as a "common password" pattern?

The checker flags passwords starting with well-known weak patterns like "password", "123456", or "qwerty".

Last reviewed: July 2026

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