Password Strength Checker

How password strength is measured

Strength comes down to entropy — the number of equally likely possibilities an attacker must search through. This tool estimates entropy from your password's length and the size of its character pool (lowercase, uppercase, digits, and symbols), then converts that into an estimated offline crack time at roughly 10 billion guesses per second.

It also penalises common passwords and obvious patterns like repeated characters or sequences (abc, 123, qwerty) — the first things real attackers try.

What makes a strong password

• Length matters most — aim for 12+ characters, ideally 16 or more
• Mix character types: lowercase, uppercase, numbers, and symbols
• Avoid dictionary words, names, dates, and keyboard patterns
• Use a unique password for every account
• A passphrase of 4+ random words is both strong and easy to remember

Understanding entropy and crack time

Entropy, measured in bits, captures how unpredictable a password is — how many equally likely possibilities an attacker would have to search. Each extra bit doubles that search space. A password drawn from a pool of 95 printable characters gains roughly 6.5 bits per character, so length has an outsized effect: a 16-character password can exceed 100 bits, far beyond what brute force can defeat. That's why this tool doubles as a simple password entropy calculator — it shows the exact bit value, not just a vague 'weak/strong' label.

Crack time turns entropy into something intuitive by assuming an attacker who can try a set number of guesses per second. This tool estimates an offline attack at roughly 10 billion guesses per second — a reasonable figure for a determined adversary with good hardware. It's an order-of-magnitude guide, not a precise prediction, but it makes the gap between a weak and a strong password viscerally clear (and answers the common question, 'how long would it take to crack my password?').

Why length beats complexity

For decades people were told to pile on symbols and numbers, but the math shows length matters more than character variety. Adding one character multiplies the search space by the size of the character pool, while swapping a letter for a symbol barely changes it. A long passphrase of ordinary words can be both stronger and easier to remember than a short, cryptic string full of substitutions.

Attackers know the common tricks — capitalising the first letter, adding a number at the end, swapping 'a' for '@' — and their cracking software tries them first, so they add little real entropy. This is why modern guidance from bodies like NIST favours longer passphrases over forced complexity rules that push people toward predictable passwords.

Tips for a stronger password

• Aim for at least 12 characters, ideally 16 or more
• Prefer a passphrase of 4+ random words over a short cryptic string
• Avoid dictionary words, names, dates, and keyboard patterns like qwerty
• Use a unique password for every account so one breach doesn't cascade
• Let a password manager generate and store long random passwords for you

Key features

• Estimates entropy in bits from length and character-pool size
• Calculates an estimated offline crack time
• Penalises common passwords and predictable patterns
• Shows a clear checklist of the criteria your password meets
• Updates instantly as you type
• 100% private — the password is never sent, logged, or stored

Who uses the password strength checker

Individuals sanity-check a password before relying on it, seeing at a glance whether it would survive an offline attack — the crack-time estimate makes the case for a longer password better than any warning. Developers and security teams use it as a teaching aid to show how entropy, length, and patterns affect strength. Trainers use the live feedback in workshops to demonstrate, in real time, how adding a word or two turns a weak password into a strong one.

Why choose our password strength checker

It's completely free — no signup, no limits, no subscription. And because it's a security tool, this matters: the entire analysis runs in your browser in JavaScript, so your password is never transmitted, logged, or stored. Unlike some 'how secure is my password' tools that send your password to a server to check breach databases, this one never sends anything — close the tab and it's gone.

It's one of 200+ free tools on ToopTools, and you can pin it to your personalized workspace, where you keep the tools you use most in one place. Next to the passphrase, PIN, and token generators, the strength checker lets you create a credential and immediately verify how strong it is — all in one spot.

Is it safe to type my password here?

Yes. The analysis runs entirely in your browser with JavaScript, so your password is never sent to a server, logged, or stored. It stays on your device and disappears the moment you close the tab.

How long would it take to crack my password?

Type your password and the tool estimates the crack time for an offline attack at about 10 billion guesses per second. Short passwords can fall in seconds; a 16-character password or a 4-word passphrase can take centuries.

What is a good entropy value for a password?

As a rough guide: under 50 bits is weak, 60–80 bits is reasonable for most accounts, and 100+ bits is very strong. Higher is always better, and adding length is the easiest way to increase it.

Does adding symbols really help, or is length better?

Symbols enlarge the character pool slightly, which helps a little — but adding length helps far more. A long passphrase usually beats a short password padded with symbols, and it's easier to remember.

Should I reuse a strong password across sites?

No. Even a strong password becomes a liability if reused, because a breach at one site exposes every account that shares it. Use a unique password per account, ideally managed by a password manager.

Is the crack-time estimate accurate?

It's an order-of-magnitude estimate based on an assumed offline attack speed, not a precise figure. Real speed depends on the hashing algorithm and hardware, but it reliably separates weak passwords from strong ones.

Is the password strength checker free?

Yes — completely free, with no account, no sign-up, and no usage limits. Test as many passwords as you like at no cost.