Password Strength Checker
Test how strong your password is in real time. See entropy in bits, crack time estimate, and specific weaknesses. Your password is never sent anywhere — all analysis happens in your browser.
🔐 What This Tool Does
A free online password strength checker that analyzes any password you enter and shows you exactly how strong it is, how long it would take an attacker to crack it, and what specific weaknesses it has. Everything runs in your browser — your password is never sent, stored, or logged anywhere.
Unlike many password checkers online that could theoretically log the passwords you type, this one is verifiably browser-based. Open your browser's DevTools, go to the Network tab, and type a password — you'll see zero network requests. You can even disconnect from the internet after the page loads and the checker will still work.
📊 What Each Metric Means
Length
The single most important factor. Every additional character makes the password exponentially harder to crack. Aim for 14+ characters.
Entropy (bits)
A measure of unpredictability. Each bit doubles the number of guesses needed. 60+ is strong, 80+ is very strong, 100+ is practically uncrackable.
Character Pool
How many distinct characters could be used. Lowercase only = 26, adding numbers = 36, adding uppercase = 62, adding symbols = ~94.
Crack Time
Estimated time for a professional attacker with GPU hardware to brute-force the password (10 billion guesses/sec assumption).
🛡️ Strong Password Best Practices
- 14+ characters minimum — length is the single biggest factor in strength
- Use a passphrase — four random words ("correct horse battery staple") is stronger than "P@ssw0rd!"
- Mix all four classes — lowercase, uppercase, numbers, and symbols
- Never reuse passwords — one breach compromises every site that shares that password
- Avoid personal info — names, birthdays, pet names, favorite sports team are the first thing attackers try
- Use a password manager — 1Password, Bitwarden, KeePass — let the manager generate and remember unique random passwords for every site
- Enable 2FA — two-factor authentication protects you even if your password is stolen
🔒 Privacy Guarantee
- ✓ Password analyzed entirely in your browser using JavaScript
- ✓ Zero network requests when typing (verify in DevTools)
- ✓ No tracking, no analytics on the input field
- ✓ No storage — close the tab and it's gone
- ✓ Works offline after page first loads
❓ Frequently Asked Questions
Is my password sent anywhere when I type it?
No. All checking happens entirely in your browser using JavaScript. Your password is never sent to any server, stored, logged, or transmitted. You can verify this by opening your browser DevTools → Network tab — you will see zero requests when you type in the password field. You can also disconnect from the internet after the page loads and the checker still works.
How do you calculate password strength?
We compute several factors: length (longer is exponentially stronger), character class diversity (uppercase, lowercase, numbers, symbols), entropy in bits (log2 of the total number of possible passwords of this length and character pool), common password detection (passwords found in major breaches), and pattern detection (sequential keys like "qwerty", repeated characters, number sequences).
What is password entropy?
Entropy is a measure of how unpredictable a password is, expressed in bits. Each bit doubles the number of possibilities an attacker has to try. A password with 40 bits of entropy has about a trillion possibilities. 60 bits is strong, 80+ bits is very strong. Entropy is calculated as length × log2(character pool size). A 12-character password using all 4 classes has about 79 bits of entropy.
How is the "crack time" estimated?
We assume an offline attacker with specialized hardware capable of 10 billion guesses per second — a realistic rate for modern GPU cracking rigs against fast hashes like MD5 or SHA-1. The crack time is half the total number of possible passwords (average case), divided by the guess rate. For slow modern hashes like bcrypt or Argon2, the real crack time would be millions of times longer, but 10 billion/sec is a safe worst-case estimate.
What makes a password "strong"?
Four things, in order of importance: (1) Length — aim for 14+ characters. Every extra character doubles the strength exponentially. (2) Unpredictability — avoid dictionary words, names, dates, and common patterns. (3) Character mix — use uppercase, lowercase, numbers, and symbols. (4) Uniqueness — never reuse passwords across sites. A 16-character random password using all 4 classes is effectively uncrackable for the foreseeable future.
Why is a long passphrase often stronger than a complex short password?
Because length matters exponentially. "correct horse battery staple" (28 chars, lowercase only) has about 132 bits of entropy and is effectively uncrackable. "P@ssw0rd!" (9 chars with all 4 classes) has only 59 bits and is weak. Length is the single most important factor in password strength. A long random passphrase is much stronger than a short password with lots of special characters.
Should I use a password manager?
Yes. Password managers like 1Password, Bitwarden, or KeePass let you use a different strong random password for every site without having to remember them. You only remember one master password. This is the single biggest security upgrade most people can make — it eliminates password reuse, which is how most account takeovers happen.
Is a password that passes this checker actually safe?
This checker measures theoretical strength against brute force attacks. A strong password by this metric is resistant to offline cracking attempts. However, no password protects you from phishing, malware, credential stuffing (if you reuse passwords), or database breaches of sites that store passwords improperly. Always enable two-factor authentication (2FA) on important accounts.