BYTETOOLS

Password Strength Checker

Test how strong your password is with an entropy score, a strength meter, an estimated crack time and clear tips to make it harder to guess — all offline.

  • Entropy score in bits from length and character set
  • Visual strength meter with a five-level rating
  • Estimated offline brute-force crack time
  • Detects common words, repeats and keyboard patterns
  • Actionable tips to strengthen a weak password
  • 100% private — the password never leaves your browser

How to use the Password Strength Checker

  1. 1

    Type or paste the password you want to test.

  2. 2

    Toggle 'Show password' if you want to check what you typed.

  3. 3

    Read the strength rating, entropy in bits and estimated crack time.

  4. 4

    Review the warnings about patterns, repeats and common words.

  5. 5

    Apply the improvement tips and watch the score update instantly.

About the Password Strength Checker

The ByteTools Password Strength Checker measures how hard your password would be to crack. It calculates the entropy in bits from the character set and length, spots common weaknesses like dictionary words, repeats and keyboard runs, and turns the result into a simple strength rating with an estimated time to brute-force.

It is built for anyone tightening up their accounts, IT teams setting policy and developers testing password rules. Instead of a vague 'weak' or 'strong' label, you see the actual entropy, the assumptions behind the crack-time estimate and specific improvements to make.

Your password is analysed entirely in your browser with JavaScript. It is never uploaded, logged or sent anywhere, so you can safely test real passwords. The tool even works offline once the page has loaded.

Frequently asked questions

How is password strength measured?

Strength is mainly a function of entropy, measured in bits. Entropy grows with the size of the character set you use (lowercase, uppercase, digits, symbols) and, more importantly, with length. Each extra character multiplies the number of guesses an attacker needs.

What is a good number of bits of entropy?

As a rough guide, under 40 bits is weak, 40–60 bits is fair, 60–80 bits is strong and above 80 bits is very strong for most threats. A long passphrase of several random words easily reaches 70 bits or more while staying memorable.

How accurate is the crack-time estimate?

It is an estimate based on a fast offline attacker making a set number of guesses per second against a stolen hash. Real times vary hugely with the hashing algorithm and hardware, so treat the figure as a relative guide, not a guarantee.

Why does the checker warn about dictionary words?

Attackers run word lists and common substitutions first, so a password built from a real word — even with a few numbers on the end — falls far faster than its raw length suggests. The tool lowers the effective strength when it spots these patterns.

Is it safe to type my real password here?

Yes. All analysis runs locally in your browser with JavaScript. Nothing is transmitted, stored or logged, and the tool keeps working with your network disconnected, so your real password stays on your device.

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