Password Strength Checker
See a password's entropy in bits, an estimated offline crack time, and which strength rules it meets — checked entirely in your browser.
Checked entirely in your browser — your password is never sent or stored anywhere.
Measure strength, not just rules
A password isn't strong just because it has a capital letter and a symbol. What actually matters is entropy — a measure of how many guesses an attacker would need. This checker calculates entropy from the character variety and length of your password, shows an estimated offline crack time, and tells you which common rules it meets, so you can see at a glance whether it's genuinely hard to guess.
What makes a strong password
The biggest lever is length: every extra character multiplies the search space. A long passphrase of several unrelated words often beats a short, cryptic string and is far easier to remember. Avoid names, dates and keyboard patterns — those collapse a password's real strength well below its raw entropy. Everything is analyzed locally, so you can safely test the passwords you actually use.
FAQ
How is the strength calculated?
It estimates entropy in bits from the character pool used (lowercase, uppercase, digits, symbols) and the length: length × log2(pool size). More length and more variety mean more entropy, which is the single best predictor of resistance to brute force.
How accurate is the crack-time estimate?
It assumes an offline attacker making about 10 billion guesses per second against a fast hash, and treats the password as random. A real password built from dictionary words or predictable patterns is far weaker than its raw entropy suggests, so treat the estimate as an upper bound.
Does length or complexity matter more?
Length. Adding characters increases entropy faster than adding symbol types. A long passphrase of several random words usually beats a short password stuffed with special characters — and it's easier to remember.
Is my password sent anywhere?
No. The analysis happens entirely in your browser — the password is never transmitted, logged or stored. Refresh the page and it's gone.
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