Password Strength Checker

Yes. This tool runs entirely in your browser using JavaScript. When you type, no network request is made — nothing leaves your device. You can verify this yourself by opening the browser's network inspector (F12 → Network tab) and watching that no requests fire while you type. That said, use common sense: don't type passwords on untrusted public computers or shared screens, regardless of the tool.

Adding symbols to a short or patterned password helps, but it's not enough on its own. The biggest score components are length and absence of detectable patterns. A 7-character password with symbols scores around 30–40 because it's too short — brute force can cover all 7-character combinations quickly. The fix is almost always to increase length first, then add character diversity.

Common patterns include: all the same character ("aaaaaaaa"), sequential letters or numbers ("abcd", "1234"), keyboard rows ("qwerty", "asdf", "zxcv"), the word "password" in any form (including P@ssw0rd, p@$$word), and the extremely common pattern of a capitalized word followed by numbers and an optional symbol (e.g. "Summer2024!"). These patterns are in every cracking rule list and get tested before brute force even starts.

Online attacks are limited by the server — most websites lock accounts after 5–10 failed attempts, add delays, or require CAPTCHA. This limits attackers to maybe 100 guesses per second at best. Offline attacks happen against a stolen password hash database — the attacker runs their software locally with no limits. A modern GPU can test 100 billion guesses per second against MD5 hashes. This is why a password that seems safe online can be cracked almost instantly if its hash is ever leaked in a breach.

For most accounts: aim for 75+ (Strong). For high-value accounts — email, banking, your password manager master password — aim for 85+ (Very Strong). A score of 75+ typically corresponds to a 12–16 character password using multiple character types without detectable patterns, which means 70+ bits of entropy and centuries of crack time even with fast offline attacks.

No — this tool performs local analysis only and never contacts any external service. Checking against breach databases (like the Have I Been Pwned Pwned Passwords API) would require sending your password or a hash of it over the network. That's a privacy trade-off some tools make, but this checker prioritizes keeping your password entirely on your device. For breach checking, you can use haveibeenpwned.com directly — they use a k-anonymity model where only the first 5 characters of a SHA-1 hash are sent, not your actual password.