How is password entropy calculated?

Entropy = log2(charset_size^length) = length × log2(charset_size). A 16-char password using uppercase + lowercase + digits + symbols has ~105 bits of entropy.

What crack time estimates are shown?

Estimates assume a modern GPU cluster performing 10 billion attempts per second (10^10/s). This is realistic for attackers using leaked hash databases.

Is my password sent to a server?

No. All analysis runs entirely in your browser using JavaScript. Your password never leaves your device.

What is NIST's recommendation for passwords?

NIST SP 800-63B recommends at least 8 characters (15+ preferred), checking against known breached passwords, allowing all printable Unicode, and not requiring periodic rotation without evidence of compromise.

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Password Strength Checker

Check how strong your password is — entropy score, crack time estimate, and actionable improvement tips.

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About this tool

Analyze any password's strength with a real entropy calculation (bits), estimated crack time on modern hardware, and specific tips for improvement. Shows character set coverage, common pattern detection, and NIST 800-63B compliance.

How to use

1 Type your password into the input field.
2 See the strength meter, entropy score, and estimated crack time update instantly.
3 Read the specific improvement suggestions.
4 Use the Password Generator tool to create a strong password.

Frequently Asked Questions

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