About Password Strength Checker
Check how strong your password is. See crack time estimates, character analysis, and improvement tips. 100% private — your password never leaves your browser.
How to use
- Paste or type the password into the input. Analysis runs entirely in your browser via JavaScript — nothing is sent over the network. Open DevTools Network tab while typing and you will see zero requests; this is the only safe way to evaluate a password you actually use, since any tool that POSTs your password to a server (even "just for analysis") becomes a logged record in someone else's database.
- Watch the strength meter calibrate in real time. The bar runs red (very weak, fewer than ~28 bits of entropy — instantly cracked), orange (weak, 28-44 bits), yellow (fair, 44-60), green (strong, 60-80), bright green (very strong, 80+ bits). Each bit added doubles the search space; jumping from 60 to 80 bits is roughly a million-fold increase in cracking cost.
- Read the estimated crack time, which assumes a modern GPU cluster doing roughly 10 billion guesses per second against an unsalted hash like SHA-256. Real-world numbers vary: bcrypt with cost 12 throttles to ~30 guesses per second per core, while a stolen MD5 database can hit 600 billion guesses per second on rented cloud GPUs. The estimate is the worst-case, fast-hash scenario.
- Review the per-criterion checklist below the meter. The tool flags length under 12, missing character classes (uppercase/lowercase/digits/symbols), keyboard sequences (
qwerty, asdfgh), repeated characters (aaaa1111), date patterns (1990, 06151985), and common dictionary words. Each red flag is a multiplier reducing real entropy below the math-only estimate.
- Pay extra attention to dictionary detection.
P@ssw0rd123! looks complex (12 chars, all four character classes, ~78 raw entropy bits) but maps to exactly the leetspeak substitutions every password cracker checks first. Real entropy after dictionary preprocessing is closer to 20 bits — cracked in seconds. The fix is randomness, not cleverness; a human-chosen "complex" password is almost always weaker than a random 12-char one.
- If the password fails any check, swap it. The Password Generator produces cryptographically random passwords with a guaranteed entropy floor. Generate, store in a password manager (Bitwarden / 1Password / KeePass / browser built-in), and never re-use across sites. The single most effective improvement most people can make is unique passwords per site plus 2FA on the high-value accounts.
- Use this tool to evaluate candidate passwords or check the strength of legacy passwords on accounts you might keep. Do not paste passwords you currently use anywhere you do not fully trust — this tool runs locally, but a phished clone could swap the JS for an exfiltrating version. View source if you need to verify; the analysis logic is plain JavaScript.
Frequently asked questions
Is this password checker safe to use?
Yes — your password never leaves your browser. All analysis happens locally in JavaScript. No data is sent to any server. You can verify this by checking your browser's network tab.
How is crack time calculated?
We estimate the time based on the password's character set size and length, assuming an attacker with a modern GPU cluster making 10 billion guesses per second. Real-world cracking may be faster for dictionary words or slower for truly random passwords.
What makes a strong password?
Length is the most important factor — 12+ characters significantly increases security. Mixing uppercase, lowercase, numbers, and symbols helps. Avoid dictionary words, names, dates, and common patterns. Consider using a passphrase (multiple random words connected by symbols).
Part of ToolFluency’s library of free online tools for Developer Tools. No account needed, no data leaves your device.