Password Strength Checker
Analyze password strength with entropy, crack time, and pattern detection. Your password never leaves your browser.
🔒 100% private: Analysis runs entirely in your browser. Your password is never sent to any server. You can verify in DevTools → Network tab.
🔒 100% private: Analysis runs locally. Nothing is transmitted. Combine strong passwords with 2FA for the best security.
About Password Strength Checker
A strong password is the first line of defense against account compromise. But "strong" is not intuitive: "P@ssw0rd123" looks complex but is extremely weak (common substitution pattern, only ~30 bits of entropy), while "correct-horse-battery-staple" is a 4-word passphrase with ~50+ bits of entropy and much stronger. This tool analyzes any password in real time using multiple heuristics: character pool size, entropy (bits), pattern detection (dictionary words, keyboard walks, sequential characters, repeated blocks, dates), common password lists, and estimated crack time at various attack speeds. It gives specific, actionable feedback so you can improve the password. Everything runs in your browser — your password is never transmitted or stored.
How It Works
- Type or paste a password into the input field.
- The tool analyzes it in real time (nothing is sent to a server).
- See the strength score, entropy (bits), and estimated crack time.
- Read the detailed feedback and requirement checklist.
- Improve your password based on the recommendations.
✨ Key Features
- ✓Real-time password analysis
- ✓Entropy calculation (bits)
- ✓Crack time estimate (online, offline, GPU)
- ✓Strength score (Very Weak → Very Strong)
- ✓Character variety detection (lowercase, uppercase, digits, symbols)
- ✓Pattern detection (dictionary words, keyboard walks, sequences, repeats)
- ✓Common password detection
- ✓Date and year detection
- ✓Length feedback
- ✓Requirement checklist
- ✓Copy-ready strong password suggestions
- ✓100% client-side — your password never leaves your browser
🎯 Common Use Cases
- →Checking whether a password is strong enough
- →Understanding why a password is weak
- →Learning password security best practices
- →Auditing your password manager entries
- →Teaching password security to team members
- →Verifying a password before setting it
- →Comparing the strength of multiple passwords
- →Understanding the impact of length vs complexity
💡 Advanced Tips & Pro Insights
- ▸Length beats complexity. A 16-character lowercase-only password has more entropy (~75 bits) than a 10-character mix of all character classes (~65 bits).
- ▸Passphrases (correct-horse-battery-staple) are often stronger than short complex passwords and easier to remember. Four random words ≈ 50+ bits.
- ▸Avoid common substitutions: p@ssw0rd, P@$$w0rd, l3tm31n — these are the FIRST substitutions attackers try. They add almost no entropy.
- ▸Never reuse passwords. A strong password that is reused across sites is one breach away from compromising every account.
- ▸Use a password manager (Bitwarden, 1Password, KeePass). Let it generate 20+ character random passwords for each site. You only need to remember one strong master password.
- ▸Enable 2FA (two-factor authentication) everywhere. It is the single most effective additional layer beyond a strong password.
Frequently Asked Questions
Is this password strength checker free?▾
Yes, this password strength checker is completely free with no signup, email, or usage limits.
Is it safe to check my real password?▾
Yes — this tool runs entirely in your browser using JavaScript. Your password is never transmitted, uploaded, or logged. Nothing leaves your device. Still, as general best practice, avoid typing production passwords into any online tool unless you control the environment.
How is strength calculated?▾
Strength is based on several factors: entropy (bits) calculated from character pool size and detected patterns, presence of dictionary words, common password matches, keyboard walks (qwerty), sequential characters (abc, 123), repeated blocks, dates, and length. The final score combines all of these.
What is entropy in a password?▾
Entropy (measured in bits) is a measure of how unpredictable a password is. It is calculated as length × log2(pool_size). Higher bits = harder to crack. 40 bits is weak, 60 bits is strong, 80+ bits is very strong.
What is the crack time estimate?▾
The crack time is an estimate of how long a brute-force attack would take at a given speed. Online attacks (rate-limited) are ~10 guesses/sec. Offline attacks (fast hash, like MD5) are up to 100 billion guesses/sec on modern GPUs. Real websites should use slow hashing (bcrypt, Argon2) making offline attacks much slower.
Why is "P@ssw0rd123" weak?▾
Despite looking complex, it is a common pattern: dictionary word "password" with a common substitution (@ for a, 0 for o) plus a sequential number (123). Attackers have these exact patterns in their rules — it is cracked almost instantly despite the "complexity".
What is a good password length?▾
For most sites, 16+ characters is a good balance. For critical accounts (email, banking, password manager), use 20–30 characters. Longer is always better — length beats complexity.
Does this tool send my password anywhere?▾
No. Your password is never transmitted over the network. The analysis runs entirely in your browser. You can verify by opening the browser DevTools → Network tab — you will see no requests containing your password.