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Password Strength Checker

Check how strong a password is based on its length, character variety, and common security patterns. Review the score, see what is missing, and improve the password before using it in important accounts.

Strength overview

Very Weak
Score: 0/100
Length
0
Character types
0/4
Repeated patterns
None

Checklist

  • At least 12 characters
  • Contains uppercase letters
  • Contains lowercase letters
  • Contains numbers
  • Contains symbols
  • Avoids common weak patterns

Suggestions

Enter a password to see suggestions for improving it.

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Coding Tools

Password Strength Checker — Test How Secure Your Password Really Is

Most people have a reasonably accurate intuition about which passwords are obviously weak — 123456, password, a pet's name, a birthday. What's much harder to judge is where passwords that feel secure actually fall on the spectrum. P@ssw0rd1! has uppercase letters, lowercase letters, numbers, and symbols — it would pass almost every legacy "must include" rule. It also appears in every major password cracking wordlist because the substitution pattern (@ for a, 0 for o, ! at the end) is so well-known that attackers build it directly into their dictionary attack rules. Real password strength is about entropy — the actual unpredictability of the password — not about whether it superficially meets a complexity checklist. This tool analyzes the factors that genuinely determine how difficult a password is to crack, and shows you specifically where it's strong and where it has weaknesses.

The entire analysis runs locally in your browser. Your password is never transmitted to any server, logged, or stored anywhere. It's safe to use this tool to check passwords for any account — though as a cautious practice, consider testing with a similar-pattern password rather than the exact one you're planning to use.

What Actually Determines Password Strength

Password strength is fundamentally about the size of the search space an attacker must cover — technically called entropy, measured in bits. Higher entropy means more possible passwords, which means longer cracking time. Two factors control entropy:

Length: This is the dominant factor by a significant margin. Each additional character multiplies the number of possible passwords by the size of the character set. A password drawn from 94 printable ASCII characters that's 8 characters long has 94⁸ possible values — roughly 6 quadrillion. The same character set at 16 characters has 94¹⁶ possible values — approximately 37 septillion. That's not a linear difference; it's an exponential one. The NIST Digital Identity Guidelines (SP 800-63B) explicitly recommend length as the primary driver of password quality, and recommend allowing passwords up to at least 64 characters.

Character variety: Drawing from a larger character set (adding uppercase, symbols, digits) increases the multiplier for each character position. An all-lowercase password uses a 26-character alphabet. Adding uppercase doubles it to 52. Adding digits and symbols pushes it toward 94. This matters, but length matters more — a 12-character lowercase-only password has more entropy than an 8-character password with full character variety.

Randomness: Entropy calculations assume random selection. A password generated by a random password generator has its theoretical entropy fully realized. A password created by a human — even one that looks complex — typically has patterns that reduce actual entropy. Common substitutions, predictable capitalizations, and word-based structures are all patterns that attackers exploit.

How Password Cracking Actually Works

Understanding attack methods helps put strength ratings in context. Attackers rarely crack passwords in real time against a live login form — rate limiting and lockouts make that impractical. The more common and dangerous scenario is an offline attack: an attacker obtains a database of hashed passwords (through a data breach) and runs cracking software locally, making millions or billions of attempts per second without any rate limiting.

Dictionary attacks: Attackers start with wordlists containing millions of common passwords, words, and phrases — including passwords from previous breaches. If your password appears in any breach database, it will be cracked almost immediately regardless of how complex it looks.

Rule-based attacks: Password cracking tools like Hashcat apply transformation rules to dictionary entries: capitalize the first letter, add 1 or ! at the end, substitute @ for a, 3 for e, 0 for o. These rules are derived from studying how real people actually modify passwords to meet complexity requirements. P@ssw0rd! is a rule-based transformation of "password" and is one of the first patterns any serious attacker tests.

Brute force: For shorter passwords, exhaustively trying every combination is feasible. Modern GPU-accelerated cracking hardware can test billions of combinations per second against certain hash types. An 8-character password using full ASCII characters can be cracked offline in hours to days. A 16-character truly random password would require centuries even with powerful hardware and fast hashing algorithms.

Passphrases — The Case for Length Over Complexity

One of the most important advances in password security thinking over the past decade is the recognition that long passphrases — sequences of random words — can be more secure and far more memorable than short mixed-character passwords. The XKCD comic "correct horse battery staple" illustrated this memorably: four random common words create a password that's long enough to have enormous entropy, while being genuinely memorable because the words create mental images.

The key requirement is that the words must be chosen randomly. "I love my dog Max" is not a good passphrase because it's personally meaningful and guessable from your social media. Four words chosen by rolling dice on a wordlist (the Diceware method) or generated by a password manager are genuinely random. A 5-word Diceware passphrase has approximately 64 bits of entropy — more than most mixed-character passwords people actually create.

For accounts where you must type the password manually (device unlock, primary email login, password manager master password), a passphrase is often the most practical choice. For other accounts, use a password manager to generate and store 20+ character random passwords that you never need to type or remember.

Password Strength Is One Part of Account Security

A strong password is essential but not the entire picture. Strong passwords are defeated every day by phishing (users typing their password into a fake site), credential stuffing (passwords from one breach being tested against other sites), and malware. The broader security practices that complement strong passwords:

Unique passwords for every account: If you use the same password on multiple sites and one of them is breached, every account using that password is compromised. A password manager makes unique passwords for every site practical.

Multi-factor authentication (MFA): Even a perfect password is compromised if it's phished or leaked. MFA adds a second factor — a time-based one-time code, a hardware key, or a push notification — that an attacker can't access even with your password. Enable MFA on every account that supports it, especially email, financial accounts, and developer tools.

Password managers: Tools like Bitwarden (open source), 1Password, and KeePass generate, store, and autofill strong unique passwords for every account. The master password and MFA protect the vault. Using a password manager eliminates the impossible trade-off between security and memorability.

Frequently Asked Questions About Password Strength

No. The entire analysis runs in your browser using JavaScript. Your password is never sent to any server — it stays on your device. This makes it safe to check passwords for sensitive accounts, though as a best practice, avoid typing actual live passwords into any web tool — generate a test password with similar characteristics instead.
Yes. aaaaaaaaaaaaaaaaa is 17 characters long but trivially weak because it's a single repeated character. passwordpassword is also long but is just a common word doubled. Length helps, but only when combined with genuine randomness or variety. Dictionary words repeated or concatenated predictably don't provide the entropy that the character count suggests.
A strong password is a solid foundation, but for accounts that matter — email, banking, cloud infrastructure, developer accounts — you should also enable multi-factor authentication (MFA). With MFA, even if your password is somehow compromised, an attacker still can't access your account without the second factor. A strong unique password plus MFA is the recommended baseline for any important account.
A passphrase is a sequence of random words used as a password — for example, maple-thunder-quiet-river. Passphrases are long (making them hard to brute force), easier to remember than random character strings, and genuinely strong when the words are chosen randomly. A traditional password is typically a shorter string with mixed character types. For accounts where you need to type the password manually (like a device login), passphrases are often the better choice.
Yes. Password managers (Bitwarden, 1Password, Dashlane, KeePass) generate long random passwords, store them securely, and autofill them — removing the need to remember or retype passwords. This makes it practical to have a unique, strong password for every account without any memory burden. The alternative — reusing passwords or using simple ones to remember them — is a far greater security risk than any concern about the manager itself.
Current guidance from NIST (National Institute of Standards and Technology) no longer recommends mandatory periodic password changes — frequent forced rotations lead users to make predictable incremental changes (Password1 → Password2) that don't improve security. Instead, change passwords when there's a specific reason: a service you use has been breached, you suspect your credentials were compromised, or you shared a password and no longer want others to have access.
Have I Been Pwned (haveibeenpwned.com) lets you check if your email address or a specific password has appeared in known data breaches. Their Pwned Passwords database contains billions of passwords from real-world breaches and uses a privacy-preserving k-anonymity model so you can check without sending your full password to any server. Many password managers also integrate this check automatically and alert you if a stored password appears in breach data.