Password Strength Checker
Evaluate your password security with our Password Strength Checker. Type any password to see its strength rating, estimated crack time, and specific suggestions for improvement. The tool analyzes password length, character variety, common patterns, and dictionary words to provide accurate security assessments. Perfect for testing new passwords before using them, auditing existing credentials, or learning what makes passwords strong. See real-time feedback as you type, helping you create stronger passwords through immediate guidance. The checker uses proven scoring algorithms and pattern analysis to estimate entropy and resistance to brute-force attacks. All analysis happens locally in your browser—passwords are never stored, logged, or transmitted anywhere. Ideal for improving personal security hygiene and understanding password best practices.
How it works: Analyzes password strength based on length, character variety, and common patterns. A strong password should be at least 12 characters with personal information. Never reuse passwords across sites.
Overview
Evaluate your password security with our Password Strength Checker. Type any password to see its strength rating, estimated crack time, and specific suggestions for improvement. The tool analyzes password length, character variety, common patterns, and dictionary words to provide accurate security assessments. Perfect for testing new passwords before using them, auditing existing credentials, or learning what makes passwords strong. See real-time feedback as you type, helping you create stronger passwords through immediate guidance. The checker uses proven scoring algorithms and pattern analysis to estimate entropy and resistance to brute-force attacks. All analysis happens locally in your browser—passwords are never stored, logged, or transmitted anywhere. Ideal for improving personal security hygiene and understanding password best practices.
About
About Password Strength Checker
Evaluate your password security instantly. Type any password to see its strength rating, estimated crack time, and specific suggestions for improvement. The tool analyzes length, character variety, patterns, and dictionary words to help you create stronger, more secure passwords.
Features:
- Real-time strength analysis
- Visual strength meter
- Specific improvement suggestions
- Pattern detection
- 100% private - passwords never sent
FAQ
Do you store my password?
No. Checks run locally in your browser.
How is strength estimated?
We use a proven scoring library and pattern analysis for entropy estimates.
How can I improve strength?
Use longer passwords with varied characters and avoid common words.
Related Tools
What Is Password Strength?
Password strength is a measure of how resistant a password is to guessing and brute-force attacks. It is typically quantified as entropy — measured in bits — which represents the number of guesses an attacker would need to crack it. A password with 40 bits of entropy requires 240 (≈1 trillion) guesses to crack with certainty. Modern GPU-based crackers can attempt billions of guesses per second, so entropy targets of 60–80+ bits are recommended for sensitive accounts.
This checker analyses your password's character set diversity, length, and patterns to estimate its entropy and crack time. It uses the zxcvbn-style approach of checking for common patterns (dictionary words, keyboard walks, repeats, dates) rather than just character set size — giving a realistic rather than optimistic strength estimate.
How to Use the Password Strength Checker
- Type or paste your password into the input field.
- The strength meter and entropy score update in real time.
- Review the estimated crack time at different attack speeds.
- Check the specific weaknesses flagged (dictionary words, short length, etc.).
- Improve the password based on feedback, or use the Password Generator for a strong alternative.
Your password is never sent to any server — all analysis happens locally in your browser.
Worked Example: Password Strength Analysis
password123 ~7 bits entropy — cracks instantly. Dictionary word + sequential numbers.
P@ssw0rd! ~15 bits — cracks in seconds. Common substitution pattern (a→@, o→0).
correct-horse-battery ~40 bits — cracks in hours/days. Three common words, predictable.
tr0ub4dor&3 ~28 bits — cracks in minutes. Mixed case + substitution still weak.
Xk#9mQ!2pLw& ~72 bits — centuries to crack. Random mixed characters, 12 chars.
Lesson: length and true randomness matter far more than simple character substitution.
Password Entropy Reference
| Password Type | Entropy (bits) | Crack Time (10B guesses/sec) | Security Level |
|---|---|---|---|
| 6-char lowercase only | ~28 | < 1 second | Very Weak |
| 8-char lowercase only | ~38 | ~3 minutes | Weak |
| 8-char mixed case + numbers | ~48 | ~1 day | Fair |
| 12-char mixed + symbols | ~79 | ~500 years | Strong |
| 16-char random mixed | ~105 | Trillions of years | Very Strong |
| 4-word passphrase (random) | ~51 | ~10 days | Good |
| 6-word passphrase (random) | ~77 | ~300 years | Strong |
Key Concepts: How Password Cracking Works
Dictionary attacks. The most common first step in password cracking uses lists of known passwords and common words. The RockYou dataset (2009 breach, 14 million passwords) and haveibeenpwned's 800 million+ exposed password list are used to instantly identify any password that was ever used by someone else. If your password exists in any breach database, it will be cracked in milliseconds regardless of its apparent complexity.
Brute-force and hybrid attacks. After dictionary attacks, crackers apply rules: adding numbers to the end, substituting letters (a→@, e→3, o→0), capitalising the first letter, appending years. These “mangling rules” mean that “Password1” and “P@ssw0rd” are trivially cracked even though they appear complex. Modern GPU rigs (like an RTX 4090) can attempt 100 billion+ MD5 hash guesses per second — making anything under 50 bits of entropy vulnerable.
Why passphrases work. A random sequence of 5–6 common words provides ~60–77 bits of entropy (depending on word list size) while being far easier to memorise than a random character string. The key word is “random” — “correct horse battery staple” (popularised by xkcd) is no longer safe since it's in every cracker's dictionary. Use a truly random word generator (like the password generator tool) to create secure passphrases.
Tips for Creating and Managing Strong Passwords
Use a password manager. The best password practice is to have a unique, randomly-generated password for every account — something impossible to remember manually. A password manager (Bitwarden, 1Password, Dashlane) generates and stores strong passwords behind a single master password. You only need to remember one strong password and the manager handles the rest. This is the single most impactful security improvement most users can make.
Enable two-factor authentication. Even a strong password can be stolen through phishing, data breaches, or malware. Two-factor authentication (2FA) adds a second layer: even if an attacker has your password, they also need your phone or hardware key. TOTP apps (Google Authenticator, Authy) or hardware keys (YubiKey) are far more secure than SMS 2FA. Enable 2FA on every account that supports it.
Never reuse passwords. Password reuse is one of the most dangerous practices. When a service is breached, attackers immediately try stolen credentials across all major sites (credential stuffing). If you reuse your email + password combination across multiple services, a breach of any one service compromises all others. Check your email on haveibeenpwned.com to see if your credentials have been exposed in known breaches.
Frequently Asked Questions
How is password entropy calculated?
Entropy (in bits) = log₂(character set size^length). For a random 12-character password using uppercase + lowercase + numbers + symbols (95 total characters): log₂(95^12) ≈ 78.8 bits. However, realistic entropy calculators also check for patterns (dictionary words, keyboard walks, common substitutions) that reduce effective entropy. A password that looks complex may have far lower practical entropy than its character set suggests.
What is a good password entropy target?
For online accounts protected by rate-limited login forms: 40–50 bits is adequate (attackers can't try billions of guesses per second). For passwords protecting locally-stored files or hashed credentials that an attacker has offline access to: 70–80+ bits. For master passwords to password managers or encryption keys: 80–100+ bits. NIST (National Institute of Standards and Technology) recommends a minimum of 8 characters but prioritises length over complexity rules.
Is my password sent to your server when I check it?
No. All password strength analysis in this tool happens entirely within your browser using JavaScript. Your password never leaves your device. You can verify this by disconnecting from the internet and using the tool — it continues to work perfectly. Never enter passwords into web tools that require server-side processing.
What makes character substitutions (a→@) weak?
Common substitutions (a→@, e→3, o→0, s→$, i→1) are well-known to attackers and are the first rules applied in hybrid dictionary attacks. 'P@ssw0rd' is cracked almost instantly because every cracker automatically tests all common substitution variants of 'password'. These substitutions provide very little real security while making passwords harder to type. True randomness always beats clever substitutions.
How do I create a strong password I can remember?
Use a random passphrase of 5–6 words from a large word list (generated randomly, not chosen). Or use a memorable sentence and take the first letter of each word + numbers/symbols. Better yet, use a password manager and only remember one strong master password. For the master password, a 6-word Diceware passphrase (generated by rolling real dice with a word list) provides ~77 bits of entropy and is memorisable.
How long does a password take to crack?
It depends entirely on the attack method and hardware. Online attacks (login forms): limited to a few guesses per second — even a weak password may take months. Offline attacks (cracking a stolen hash): an RTX 4090 attempts ~100 billion MD5 guesses/second. At that rate: 6-char lowercase = under 1 second, 8-char lowercase = 3 minutes, 10-char mixed = years, 12-char mixed + symbols = 500+ years. Modern algorithms (bcrypt, Argon2) are deliberately slow to cracking.
What is credential stuffing?
Credential stuffing is an automated attack where stolen username/password pairs from one breach are tried against many other sites. After the 2012 LinkedIn breach exposed 117 million passwords, attackers immediately tried those credentials on Netflix, Gmail, Amazon, and hundreds of other services. Millions of accounts were compromised this way. The only defence is unique passwords for every account — which is why password managers are essential.
Should I change passwords regularly?
NIST's 2020 guidelines reversed the traditional advice to change passwords regularly. Frequent forced changes lead to predictable patterns ('Password1!' → 'Password2!') and users choosing weaker passwords. Current best practice: use strong, unique passwords and only change them when there's evidence of compromise (breach notification, suspicious activity). Enable notifications from services like haveibeenpwned.com to know when your credentials appear in new breaches.