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Password Strength Meter

100% Free

An entropy-first password meter: see your password's bits of entropy, keyspace size, a 0–100 score, and estimated crack time under five attacker scenarios — live, in-browser.

Entropy Score
5 Attack Models
0–100 Meter
100% Client-Side

1. Enter your password

Runs entirely in your browser. Nothing you type is uploaded, logged, or stored.

2. Strength score

Enter a password to see its entropy, keyspace, and crack-time estimates.

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Add Password Strength Meter to your website or blog in seconds.

  • Responsive design
  • Lightweight & fast
  • No backend required
  • Always up-to-date 
<iframe
  src="https://tools.town/embed/password-strength-meter/"
  width="100%"
  height="600"
  style="border:none; border-radius:12px;"
  loading="lazy"
  title="Password Strength Meter">
</iframe>

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How to Use

  1. 1 Type or paste the password you want to measure
  2. 2 Read the 0–100 entropy score on the gauge
  3. 3 Check the entropy in bits and the keyspace magnitude
  4. 4 Compare estimated crack time across five attacker models
  5. 5 Apply the tips to push the score higher

Features

  • 0–100 score derived directly from entropy
  • Entropy in bits and keyspace size (powers of ten)
  • Crack-time estimates for five attacker scenarios
  • Live gauge that updates as you type
  • Improvement tips for missing character classes
  • 100% client-side — your password never leaves the browser

Why it Matters

Most strength meters give a vague label. Seeing the actual entropy in bits and how crack time changes between a throttled online attack and a GPU array makes the trade-offs concrete — and shows exactly why one more character matters more than one more symbol.

★★★★★

Use Cases

Security-Conscious Users

Measure real entropy, not a vague label

Developers

Sanity-check password policy thresholds

Educators

Show how entropy and crack time relate

Password Hygiene

Tune a passphrase until the score saturates

What this tool does

The Password Strength Meter measures a password the way a cryptographer would: it computes the entropy in bits, the size of the keyspace, a 0–100 score, and the estimated crack time under five different attacker models — from a throttled online login to a massive offline cracking array.

How it works

The meter determines your password’s character pool (lowercase, uppercase, digits, symbols), computes entropy as length × log2(poolSize), and derives the keyspace magnitude and a normalised score. Crack time for each scenario is the keyspace (halved for the average case) divided by that attacker’s guess rate.

Checker vs meter

The Password Strength Checker gives a quick, rule-based checklist; this meter is the numbers-first companion. Use them together — the checklist for fast guidance, the meter to understand exactly why.

Privacy

Everything runs in your browser with JavaScript. Your password is never uploaded, logged, or stored.

Frequently Asked Questions

What is password entropy?
Entropy measures unpredictability in bits. It equals the password length multiplied by log2 of the character pool size. Each extra bit doubles the number of guesses an attacker needs, so higher entropy means exponentially more resistance to brute force.
Why show five attacker scenarios?
Crack time depends entirely on how fast the attacker can guess. A throttled online login allows ~100 guesses/second; a GPU cracking stolen fast hashes can do tens of billions. Showing the range makes it clear that the same password can be 'safe' online yet weak against an offline dump.
How is the 0–100 score calculated?
The score scales linearly with entropy, reaching 100 at about 80 bits — the point where even a massive offline array would need an impractical amount of time. It's a tuning guide, not an absolute guarantee.
How is this different from the Password Strength Checker?
The checker is rule-based with a pass/fail checklist; this meter is entropy-first and number-heavy, showing bits, keyspace, and multiple crack-time models. Use the checker for quick guidance and the meter to understand the math.
Is my password sent anywhere?
No. Everything is computed in your browser with JavaScript. Your password is never uploaded, logged, or stored.
📖

Want to learn how this works?

Browse all guides →
Password Entropy Explained
entropy

Password Entropy Explained: Bits, Keyspace & Crack Time

What password entropy actually measures, how to compute it from length and character pool, why crack time depends entirely on the attacker, and how to read an entropy-based strength meter.

25 Jun 2026

5 min read

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