Password Strength Checker & Generator — Free Online Tool
Check how strong your password is and generate secure passwords instantly. See real-time feedback on entropy, crack time, breach status, and common pattern detection. Nothing is stored or transmitted. 100% client-side — passwords never leave your browser.
How to Use the Password Strength Checker
- Type or paste a password in the input field — strength updates in real-time.
- Read the strength meter — it shows entropy bits, crack times at different attack speeds, and breach status.
- Review suggestions to improve weak passwords before using them.
- Use the random generator to create a secure password with custom character options.
- Try the passphrase generator to create memorable, strong passphrases from random words.
Why Use This Password Strength Checker
"Password123!" looks strong to a human — it has uppercase, lowercase, numbers, and a symbol. But it's in every password dictionary and would be cracked in milliseconds. This tool uses entropy analysis, dictionary detection, keyboard/sequential pattern detection, and the Have I Been Pwned breach database to give you a realistic assessment, not just a checklist.
It's essential for security audits, user registration flows, and personal password hygiene. The generator creates truly random passwords that are both strong and memorable when you use the passphrase option.
Frequently Asked Questions
Length is the most important factor — a 20-character password with mixed characters has billions of years of crack time, even with brute force. Beyond length: use a mix of character types, avoid dictionary words and common patterns (like "password123" or "qwerty"), and never reuse passwords across sites. Also check it against breach databases.
It uses the Have I Been Pwned k-anonymity API: your password is hashed with SHA-1, and only the first 5 characters of the hash are sent to the API. The API returns all hash suffixes matching that prefix — the check happens entirely in your browser. Your actual password is never transmitted.
Entropy measures password strength in bits using the formula: log2(pool_size^length). The pool size depends on character types used (26 lowercase, 52 upper+lower, 62+numbers, 94+symbols). More entropy = harder to crack. 80+ bits is considered strong; 128+ is excellent.
Absolutely. Use this tool to generate a strong master password (20+ characters), then let a password manager generate and store unique passwords for every account. You only need to remember one strong password. Password managers are the single most impactful security improvement for most people.
Yes — passphrases like "correct-horse-battery-staple" are both strong and memorable. They work because of length (4 words = 40+ characters) rather than complexity. Use 4-6 random words from a large wordlist for maximum security with minimum memorization effort.
Use Cases
Testing Password Strength
Check password strength before creating accounts to ensure your credentials are secure.
Breach Detection
Check if your password appears in known data breaches using the Have I Been Pwned database.
Secure Password Generation
Generate cryptographically secure random passwords with customizable length and character types.
Memorable Passphrases
Create strong, memorable passphrases using random words for easy-to-remember security.
Auditing Team Policies
Verify that team password policies meet security standards and compliance requirements.