Password Strength Tester — Entropy & Crack-Time Estimate

Password Strength Tester

100% free · Runs 100% in your browser · No signup needed

Try an example: test “Tr0ub4dor&3”

Sobre Password Strength Tester

Is Your Password Actually Strong?

Most people judge password strength by gut feeling — and gut feeling is terrible at it. "P@ssw0rd!" looks complex, but it is one of the first guesses any attacker tries. Real password strength is measurable: it comes down to entropy (how many possibilities an attacker must search) and to whether the password contains patterns attackers exploit. The Password Strength Tester on fisthost.com/tools measures both, giving you an entropy score in bits, an estimated crack time, and a specific list of weaknesses — all computed locally in your browser, with your password never leaving your device.

How Strength Is Measured: Entropy Bits

Entropy quantifies unpredictability. The formula is simple:

entropy bits = length × log₂(character-pool size)

The pool depends on which character types the password uses:

Character types used	Pool size	Bits per character
Lowercase only	26	~4.70
Lower + uppercase	52	~5.70
Letters + digits	62	~5.95
Letters + digits + symbols	~94 (printable ASCII)	~6.55

Example: a 12-character password drawn from all 94 printable ASCII characters has about 12 × 6.55 ≈ 78.6 bits of entropy. That is a genuinely strong password — if it is random. But entropy alone is not the whole story, because humans are not random.

Estimated Crack Time — Read the Fine Print

From entropy, the tool estimates how long a brute-force attack would take. The math: an attacker needs, on average, 2^{(bits−1)} guesses to find the password. Assuming roughly 10 billion guesses per second (a plausible offline GPU attack), the tool converts that into seconds, hours, years, or centuries.

Crucially, this is a rough estimate, never an exact prediction. Real attack speed depends on the hashing algorithm, the attacker's hardware, and whether they use smarter methods than brute force (they do — see below). Treat the number as an order-of-magnitude guide: "centuries" means comfortable, "minutes" means change it now.

Beyond Entropy: The Checks That Catch Human Passwords

Attackers do not start with brute force. They start with the passwords humans actually choose. The tester checks for:

• Common passwords — a built-in list including "password", "123456", "qwerty", "letmein", and hundreds more. If your password is on any attacker's list, its effective entropy is near zero.
• Keyboard sequences — "qwerty", "asdf", "zxcvbn" and their shifted variants are in every cracking dictionary.
• Sequential runs — "1234", "abcd", "9876" are trivially predictable.
• Repeated characters — "aaa", "1111" add length without adding unpredictability.
• Common substitutions — "P@ssw0rd" fools no one; crackers apply leetspeak rules automatically.

Each weakness found is listed explicitly, so you know exactly what to fix rather than guessing.

What the Tool Shows You

• Password input with show/hide toggle — test comfortably, reveal only when you choose.
• Strength meter — an at-a-glance visual rating from weak to excellent.
• Entropy in bits — the raw mathematical score.
• Estimated crack time — translated into human terms (seconds to centuries), labeled as an estimate.
• Specific weaknesses list — every detected pattern, named.
• Actionable tips — concrete next steps to strengthen the password.

The Honest Labels That Matter

Three promises this tool makes — and keeps:

1. 100% client-side. Your password NEVER leaves your browser. The analysis runs in JavaScript on your device; nothing is uploaded, logged, or stored. You can verify this by testing with your network disconnected — it still works.

2. An estimate, not a guarantee. Crack time depends on unknown attacker capabilities. The tool labels its figure as an estimate and will never display "uncrackable" or any absolute claim. No password is uncrackable — only impractically expensive to crack.

3. Strength ≠ safety alone. A strong password reused across sites, or stored insecurely, is still a liability. Strength testing is one layer of good password hygiene, not the whole of it.

Password Guidance, Per NIST SP 800-63B

The US National Institute of Standards and Technology's digital-identity guidelines reshaped modern password advice. The key takeaways the tool's tips reflect:

• Length beats complexity. A long passphrase of random words outperforms a short, symbol-stuffed password and is easier to remember.
• Use a password manager. Humans cannot memorize dozens of strong, unique passwords — managers generate and store them for you.
• Never reuse passwords. One breached site should never compromise your other accounts.
• Enable two-factor authentication wherever it is offered, ideally with an authenticator app — try the TOTP Generator to see how time-based codes work.
• Check against known breaches — if a password has appeared in a breach, retire it everywhere.

Common Password Myths, Debunked

• "Symbols make any password strong." "P@ssw0rd!" has symbols and is cracked in seconds. Length and randomness matter far more.
• "I need to change passwords every 90 days." Forced rotation leads to weaker passwords ("Spring2026!" → "Summer2026!"). NIST now advises changing only when compromise is suspected.
• "Nobody would target me." Most attacks are automated and indiscriminate — credential-stuffing bots try leaked passwords against thousands of accounts per minute.
• "My password is uncrackable." Nothing is. The goal is to make cracking cost more than the account is worth.

Protect Your Own Website's Users Too

If you run a website with user accounts, password security is your responsibility as well as your users'. Store passwords with a proper adaptive hash — never plain text, never plain MD5 or SHA-1. The Bcrypt Hash Generator shows how modern password hashing works, and the JWT Generator covers the tokens behind "stay logged in" sessions. Validating input formats is another layer — the Credit Card Validator demonstrates client-side format checking with the Luhn algorithm.

Host Your Projects Securely With FistHost

Good security starts with good hosting. FistHost shared hosting begins at just $0.99/month, and the annual plan includes a free domain for your first year — reliable servers, easy management, and support that takes security seriously. Build your site on a foundation you can trust.

Frequently Asked Questions

Is it safe to type my real password into the tester?

Yes — the tool runs entirely in your browser and your password is never transmitted anywhere. Still, as a general habit, prefer testing passwords you are considering rather than ones already in use.

What is a good entropy score?

As a rule of thumb: under 40 bits is weak, 40–60 is moderate, 60–80 is strong, and 80+ is excellent — assuming the password is genuinely random and not on a common-password list.

Why did my long password score poorly?

Probably a detected pattern — a dictionary word, keyboard sequence, or repetition. Length only helps when the characters are unpredictable; check the weaknesses list.

How accurate is the crack-time estimate?

It is an order-of-magnitude estimate based on ~10 billion guesses per second. Real attacks vary widely, so treat it as guidance, not a guarantee.

Should I use a passphrase or random characters?

Both work. Five or six random words ("correct horse battery staple" style) give strong entropy and are memorable; a password manager generating random characters is even better.

Launch Something Secure on FistHost

Whether it is a membership site, a client portal, or your next big idea, start it on hosting that takes reliability seriously. FistHost offers shared hosting from $0.99/month with a free domain on annual plans — get online today.