Password Strength Checker

Score a password against eight separate checks and see an entropy estimate in bits. The checker looks at length, whether all four character types are present, whether any character repeats three or more times in a row, and whether the password starts with one of the best known guesses.

Password

This runs entirely in your browser. Your password is never sent anywhere.

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Why use Password Strength Checker?

Password strength meters usually give you a colour and nothing else, which teaches you nothing about what to change. This one shows the eight checks separately so the gap is visible: a fifteen character all lowercase phrase fails the variety checks but scores well on length, while a short password packed with punctuation does the opposite. Entropy is the number worth watching. It measures the size of the space an attacker would have to search, expressed in bits, where each extra bit doubles the work. Because it multiplies length by the logarithm of the pool, it captures something the pass or fail checks cannot: that stretching a password is far more effective than sprinkling in symbols. Two things no strength checker can tell you. It cannot know whether your password has already leaked in a breach, and it cannot know whether you have used it somewhere else. A password that scores Strong but appears in a public dump is worthless, which is why uniqueness per account matters more than any rating on this page.

Key benefits

Eight independent checks rather than one opaque score
Entropy shown in bits, the measure that actually reflects guessing difficulty
Catches three or more identical characters in a row, a pattern simple scorers miss
Flags the handful of passwords that top every breach list
Never transmitted, so it is safe to test a password you actually use

Features

Length thresholds at 8 and 12 characters, scored separately
Character class detection for lowercase, uppercase, digits, and symbols
Entropy calculated as length multiplied by the base two logarithm of the character pool
Repeat detection and a common password prefix check
Four band rating from Very Weak through to Strong

Popular use cases

Checking a password before you commit it to a password manager
Understanding why a site rejected a password you thought was fine
Showing someone concretely why length beats added punctuation
Auditing a shared credential your team has been reusing

How to use Password Strength Checker

1
Type or paste a password
The field is masked by default. Use the show toggle if you need to read what you typed.
2
Read the eight checks
Each check passes or fails on its own, so you can see exactly which quality the password is missing.
3
Look at the entropy figure
Bits of entropy tell you how large the search space is, which matters more than the label.
4
Adjust and watch it move
Adding length usually raises entropy faster than adding one more character type.

Frequently asked questions

How is the entropy figure calculated?

The pool size is built from the character types present: 26 for lowercase, 26 for uppercase, 10 for digits, and 32 for symbols. Entropy is then the password length multiplied by the base two logarithm of that pool. A twelve character password using all four types works out around 78 bits.

Why does length matter more than adding a symbol?

Entropy scales linearly with length but only logarithmically with pool size. Going from a 62 character pool to a 94 character pool adds about 0.6 bits per character, while adding four more characters at 62 adds nearly 24 bits. Longer wins comfortably.

What counts as a repeat?

Three or more of the same character in a row, so aaa fails the check but aa passes. Runs like this shrink the effective search space because attack tools try them early.

Is it safe to type a real password here?

Yes. Every check runs in the page and nothing is transmitted, stored, or logged. That said, a general habit worth keeping is to avoid pasting live credentials into any site you have not verified for yourself.

Does a Strong rating mean the password is safe?

It means it passed all eight checks, which is a reasonable bar. It cannot tell whether the password has already appeared in a breach, because that would require checking it against a leaked password database. A unique password per account still matters more than any score.

Last reviewed: July 2026

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