A strong password is long (at least 12–16 characters), uses a mix of character types (uppercase, lowercase, numbers, and symbols), avoids dictionary words, and contains no predictable patterns. The best passwords are randomly generated strings or memorable passphrases made of unrelated words.

Our tool evaluates multiple factors: length, character variety (lowercase, uppercase, digits, symbols), absence from common password lists, and detection of weak patterns like sequences ("abc", "123"), keyboard walks ("qwerty"), and repeated characters. Each factor contributes to a score from 0–100, with entropy measured in bits to estimate crack resistance.

Password entropy measures randomness and unpredictability in bits. Each additional bit doubles the number of possible combinations. For example, a 10-character password using only lowercase letters has about 47 bits of entropy, while adding numbers and symbols can push it above 65 bits. Passwords with 80+ bits of entropy are considered extremely resistant to brute-force attacks, even with powerful hardware.

The crack time is an estimate based on an attacker making 1 billion guesses per second (typical of a modern GPU cluster attacking fast hashes like MD5). Real-world times vary: online attacks (with rate limiting) are far slower, while targeted attacks using specialized hardware can be faster. Using slow hashing algorithms like bcrypt or Argon2 dramatically increases crack resistance.

Yes — this tool runs entirely in your browser. Your password is never transmitted over the internet, stored on any server, or logged anywhere. All analysis happens locally using JavaScript. That said, it's good practice to avoid entering your actual production passwords into any third-party tool. Use a similar test password or our built-in generator to understand strength principles.

Use a password manager (like Bitwarden, 1Password, or KeePass) to generate and store unique passwords for every account. Alternatively, use the passphrase method: combine 4–6 random, unrelated words (e.g., "correct-horse-battery-staple"). Passphrases are easier to remember and can achieve very high entropy. Enable two-factor authentication (2FA) wherever possible for an extra layer of security.

The most common weak patterns include: simple number sequences ("123456", "111111"), keyboard walks ("qwerty", "asdfgh"), common words ("password", "admin", "letmein"), personal info (birthdays, names, pet names), and simple leet-speak substitutions ("p@ssw0rd"). Attackers specifically target these patterns first in dictionary attacks.

Modern security guidelines (NIST, NCSC) recommend not forcing regular password changes unless there's evidence of compromise. Frequent changes often lead to weaker passwords. Instead, use a unique, strong password for each service, enable 2FA, and only change passwords when a breach is suspected or confirmed. Check haveibeenpwned.com to see if your accounts have been compromised.