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Password Strength Checker

Type a password to see its entropy in bits and an estimated crack time against an offline attack, calculated locally, nothing you type ever leaves your browser.

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Strength
Enter a password above
Entropy
0 bits
Character pool
0
Est. crack time (offline attack)
-

Nothing you type here is sent anywhere, every calculation runs locally in your browser. Estimate assumes 10 billion guesses per second, a commonly cited benchmark for an offline attack against a stolen, unsalted password hash.

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How the entropy score is calculated

Entropy, measured in bits, estimates how many guesses an attacker with no other information would need to try before finding your password. It is calculated as the password's length multiplied by log base 2 of the character pool it draws from, lowercase letters add 26 possibilities, uppercase adds another 26, digits add 10, and symbols add roughly 32, so a longer password drawing from a bigger pool has exponentially more possible combinations to guess through.

What the crack time estimate assumes

The estimated crack time assumes an offline attack against a stolen, unsalted password hash at 10 billion guesses per second, a commonly cited benchmark for what a modern GPU rig can achieve against a fast, unsalted hashing algorithm. A well-salted, slow hash like bcrypt or Argon2 would make the same password take vastly longer to crack, this number represents a realistic worst case, not a guarantee for every system.

Why length usually beats complexity

Adding a character to a password multiplies the total number of guesses an attacker needs, while adding one more allowed symbol type only multiplies it by a much smaller factor. A long passphrase of unrelated words is typically far stronger, and much easier to remember, than a short password crammed with substitutions like swapping an letter for a number, which most modern cracking tools already account for.

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FAQ

Password Strength Checker: questions, answered

Is it safe to type my real password into this tool?
The check runs entirely in your browser using JavaScript, nothing is sent to a server, logged, or stored. That said, as a general habit it is safer to test a password of similar length and character mix rather than an actual password you use on an important account.
What guess rate does the crack time estimate use?
10 billion guesses per second, a widely cited benchmark for an offline attack using modern GPU hardware against a fast, unsalted password hash. Real-world crack time varies significantly based on the target system's actual hashing algorithm and attacker resources.
Why did a long password with only lowercase letters score lower than I expected?
Character variety matters because it expands the pool of possibilities per character. A long password using only lowercase letters, a pool of 26, still has solid entropy from length alone, but the same length using upper and lowercase letters, digits and symbols, a pool of over 90, gains entropy far faster per additional character.
Does this check against known leaked password lists?
It flags a short list of extremely common passwords, like 123456 or password, that show up constantly in breach data. It does not check against the full scale of real-world leaked password databases, which would require sending your password to an external service, something this tool deliberately never does.
What entropy is considered strong enough?
As a rough guide, under 28 bits is very weak, 28 to 59 bits is weak to reasonable, 60 to 127 bits is strong, and 128 bits or more is very strong, roughly the entropy of a long, randomly generated passphrase or password manager output.

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