Password Strength Checker

Analyze password strength with entropy, criteria checklist and improvement suggestions

What is it and how does it work?

A password strength checker estimates how hard a password would be to crack and shows you why. Rather than a vague "weak/strong" label, a good checker measures entropy — the number of guesses an attacker would need — and breaks down what helps and hurts: length, the mix of character types, and whether the password contains predictable patterns like common words, dates or keyboard runs. It turns the abstract advice "use a strong password" into concrete feedback you can act on.

The single biggest factor is length, not exotic characters. Each extra character multiplies the number of possible combinations, so a long passphrase of ordinary words beats a short string of symbols that is hard to type and easy to forget. The checker also flags the traps that make a password weak despite looking complex — a dictionary word with a number tacked on, or a predictable substitution like "P@ssw0rd". Crucially, this tool evaluates everything in your browser: your password is never transmitted, stored or logged.

Common use cases

• Vetting a new password: check a password you are about to use and see specific reasons it is weak or strong before committing to it.
• Comparing approaches: test a long passphrase against a short complex string to see which is actually harder to crack.
• Teaching good habits: demonstrate why length beats complexity by watching the strength estimate rise as you add words.

Frequently asked questions

What makes a password strong — length or special characters?

Length matters most. Each added character multiplies the possible combinations far more than swapping a letter for a symbol does. A long passphrase of several random words is typically stronger, and easier to remember, than a short string packed with symbols.

Is my password sent anywhere when I check it?

No. The analysis runs entirely in your browser, so the password is never transmitted, stored or logged. That is essential — checking a real password on a tool that uploaded it would itself be a security risk.

What is entropy and why does it matter?

Entropy measures unpredictability — roughly, how many guesses an attacker would need. More entropy means exponentially more guessing, so it is a better measure of strength than counting character types. Length and randomness raise entropy; predictable patterns lower it.

Why is "P@ssw0rd" rated weak despite the symbols?

Because it is a common word with predictable substitutions that attackers' tools try first. Real strength comes from unpredictability, not from decorating a guessable word — so a dictionary base undermines a password even with symbols and numbers added.

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