Password Strength Checker
Check how strong a password is. Enter a password to see its estimated entropy, and whether it meets common strength criteria like length, character variety, and avoiding common patterns.
No Password
Recommended Settings
Pro Tips
- •Entropy estimates how many attempts a brute-force attacker would need, based on password length and the variety of character types used
- •Length matters more than complexity for most passwords - a longer password with fewer character types can still beat a short, complex one
- •This checker also flags common passwords, obvious sequences (like "123" or "abc"), and repeated characters, which are the first things real attackers try
- •This tool checks patterns and structure - it doesn't check your password against real-world leaked password databases
Most Popular
Most users check a candidate password here before setting it as their actual account password
When to Use This Tool
Check whether an existing password meets modern strength recommendations.
Test a new password idea before committing to it for an important account.
Demonstrate what makes a password weak or strong in a training or educational setting.
Verify a password meets common organizational password policy requirements.
How It Works
Check the password against a set of criteria: length, character variety, common password lists, sequential patterns, and repeated characters
Estimate entropy by multiplying password length by the log base 2 of the character set size used
Combine the criteria into an overall score and translate that into a plain-language strength rating
100% Private
Files never leave your device. All processing happens locally in your browser.
Lightning Fast
Powered by Client-side JavaScript pattern analysis for optimal performance on modern browsers.
Open Source
Built with verified, open-source libraries. Fully transparent.
Frequently Asked Questions
Is my password sent to a server when I type it here?
No. Every check happens locally in your browser using JavaScript as you type. Your password is never transmitted anywhere, including to this website's own servers - it only exists in your browser's memory while you're using the tool.
What is password entropy?
Entropy is a measure of unpredictability, expressed in bits. Higher entropy means more possible combinations an attacker would need to try to guess your password through brute force. It's calculated from your password's length and the variety of character types used.
Does this check against real leaked password databases?
No. This tool checks structural patterns (length, character variety, common words, sequences, repeats) locally. It doesn't check your password against breach databases, since doing so securely would require sending your password to an external service.
Why is my long password rated only "Moderate"?
Length alone isn't the only factor - a long password using only lowercase letters, or containing obvious sequences or common words, will score lower than a similarly long password using varied character types with no predictable patterns.
Should I reuse a password that scores "Very Strong" across multiple accounts?
No. Even a very strong password should be unique to each account. If one site suffers a data breach, reused passwords put all your other accounts at risk too.