Password Strength Checker

The Password Strength Checker measures how hard a password would be to guess and shows the result as a clear strength rating, an entropy figure in bits, and estimated crack times against different kinds of attackers. Type or paste a password and the meter updates instantly, along with a list of specific weaknesses and suggestions for making it stronger.

Strength here is not about whether a password "looks" complicated. It is about how many guesses an attacker would need to try before landing on it. The tool estimates that search space from the length of the password and the mix of character types, then reduces the estimate when it spots patterns that make a password predictable - common leaked passwords, keyboard runs, repeated blocks, or a single character type. That gives a more honest picture than a naive checklist of "add a symbol".

Critically, the password never leaves your device. All analysis runs in your browser in plain JavaScript, with nothing typed, pasted, or generated being uploaded, logged, or stored. That means it is safe to test real passwords, and the tool keeps working with no network connection once the page has loaded. Use it to sanity-check a password before you commit to it, or to understand why a password you thought was strong might not be.

Entropy is only an honest measure when the password was generated randomly, and human-chosen passwords rarely are. Substituting characters in a familiar word looks strong to a naive character-count score and is weak in practice, because cracking tools apply exactly those substitutions as rules: P@ssw0rd1 has the shape of a strong password and appears in every wordlist. That is why pattern detection matters more than composition here. Crack-time estimates assume offline attack against a fast hash, which is the pessimistic and correct assumption for a leaked database, and they say nothing about whether the password has already appeared in a breach. Length and unpredictability are what help. A passphrase of several unrelated words beats a short string of symbols on both counts, and is far easier to type.