Password Strength Checker

Safety depends on whether checker runs client-side or server-side. Client-side checkers (like this tool) process password entirely in browser using JavaScript—password never transmitted to server, never logged, never stored. Completely safe. Server-side checkers send password to remote server for analysis—avoid these for real passwords (even if claims not to log, no verification). How to verify client-side: disconnect internet after page loads, enter password, if analysis still works (it's client-side), or check browser developer tools Network tab (should show no requests when typing password). For maximum safety: use client-side checker, verify no network activity, or use dummy password similar to real one to test, never enter current production password into unknown online tools. Best practice: bookmark trusted client-side checker, use for all password evaluation. For ultra-sensitive passwords (master password, encryption keys), use offline tools or password manager built-in analysis.

Length and symbols don't guarantee strength if password uses common patterns. Examples of long but weak passwords: dictionary phrase with substitutions ("P@ssw0rd123456!"), repeated patterns ("abcabc123123"), keyboard patterns ("qwerty123!@#"), common phrases ("ILoveYou2024!"), or predictable structures (word+number+symbol). Checker looks beyond requirements at actual entropy: dictionary words are easily guessed (billions in dictionaries), predictable substitutions (@ for a, 0 for o) don't add security, common patterns appear in attack dictionaries, and human-generated "random" isn't random. Solutions: use true random password generator, avoid any dictionary words (even with symbols), mix character order unpredictably (not all numbers at end), and increase length with random characters (not repeating patterns). Example: "P@ssw0rd123456!" has length and symbols but is Very Weak (common password + predictable pattern); "xK9#mP2$vL5@nR8" same length, truly random, Very Strong. True randomness is key.

Entropy measures password randomness/unpredictability in bits—higher entropy means more possible combinations and longer to crack. Each bit doubles possibilities: 1 bit = 2 combinations, 10 bits = 1024, 20 bits = 1 million, 40 bits = 1 trillion, 64 bits = 18 quintillion, 80 bits = 1.2 septillion, 128 bits = 340 undecillion. Entropy calculation: characterSet^length. Examples: 8 random lowercase letters = 26^8 = 37 bits (crackable), 8 random alphanumeric+symbols = 95^8 = 52 bits (weak), 12 random alphanumeric+symbols = 95^12 = 79 bits (good), 16 random alphanumeric+symbols = 95^16 = 105 bits (very strong). Why it matters: attackers use brute force trying all combinations—higher entropy = exponentially longer to crack. 40 bit password: seconds to crack, 60 bit: hours, 80 bit: years, 100 bit: centuries. Recommendation: minimum 60-bit entropy for regular accounts, 80+ for sensitive accounts, 100+ for critical systems. Note: dictionary words drastically reduce entropy—"correcthorsebatterystaple" is 25 characters but only ~44 bits entropy (dictionary attack vs brute force).

Update frequency depends on account sensitivity and threat landscape. General guidelines: Critical accounts (banking, primary email, password manager master password): check annually, update if rated below Strong, or immediately if service reports breach. Work accounts: follow corporate policy (typically 90-180 days for privileged access, annual for regular users), or when leaving company/changing roles. General accounts (social media, shopping, forums): check every 2 years, update if Very Weak or Weak, or after service breach notification. Low-security accounts: update when convenient or if compromised. Modern recommendation moving away from mandatory frequent changes (causes users to make minor predictable changes: password1 → password2) toward: use strong unique passwords initially (12+ characters, high entropy), never reuse across sites, change immediately if breach suspected, and use password manager to generate and store strong passwords. Check passwords: after major security news (new attack methods), when upgrading security (adopting password manager), during security audits, or if notice suspicious activity. Focus on uniqueness and strength over frequency—strong unique password kept years is better than weak password changed monthly.

Practically, no—stronger is always better security-wise. However, considerations: Some websites limit password length (8-32 characters common, occasionally just 16)—generate longest allowed. Very long passwords (50+ characters) offer no additional security over 20-25 character truly random password (already astronomically secure), but no harm. Memorability: if not using password manager and must memorize, very strong passwords are difficult—balance security and usability (12-16 memorable random words or 12-16 character pronounceable password acceptable if truly random). Typing effort: extremely long passwords (30+ characters) on mobile devices can be frustrating—password manager auto-fill solves this. Compatibility: some systems have issues with certain special characters (especially legacy systems)—generate without if problematic. Recommended: maximum practical length for password manager generated passwords is 20-25 characters (massive security, manageable if ever need to type manually), for memorized passwords aim for 16+ characters with maximum complexity you can remember, and use password manager to eliminate memorization need for most accounts (allowing maximum strength everywhere). Bottom line: within reason, longer and more complex is better—no such thing as too strong.