Password Strength Tester

Check how strong a password is — entropy, rating and actionable feedback, all computed in your browser.

Enter a password to testShow password

Testing happens entirely in your browser — the password is never transmitted or stored.

How to use the Password Strength Tester

Type a password. Enter or paste the password you want to evaluate into the box.
Read the rating. See its strength rating, entropy in bits, and which character types it uses.
Act on the tips. Follow the feedback to strengthen it — or generate a strong one with our Password Generator.

Why use our Password Strength Tester

Instant, private analysis. Strength updates as you type and never leaves your browser — safe to test real passwords.

Entropy in bits. See the estimated entropy, the single best measure of how hard a password is to brute-force.

Clear, actionable tips. Get specific suggestions — add length, mix character types, avoid common passwords.

Common-password check. Flags passwords found on the most-used-password lists that attackers try first.

Free to use — premium coming soon

FREE

✓ Unlimited tests
✓ Entropy & strength rating
✓ Improvement feedback
✓ Common-password detection

PREMIUM

★ Remove ads
★ Breach-database lookup
★ Bulk password auditing

About the Password Strength Tester

The Password Strength Tester estimates how resistant a password is to guessing and brute-force attacks, then gives you a clear rating and feedback you can act on. Instead of just counting whether you used an uppercase letter or a digit, it looks at the password the way a real attacker would: it flags dictionary words, common passwords, keyboard runs like 'qwerty', sequences like '1234', repeated characters, dates, and predictable letter-for-symbol swaps (such as 'p@ssw0rd'). The result is a more honest picture of risk than a meter that simply rewards adding a '!' to the end of a weak word.

Use it whenever you are about to set or change an important password, especially for email, banking, cloud storage, or a password manager's master password. It is also handy for sanity-checking a passphrase before you commit it to memory, or for teaching family members and coworkers why 'Summer2025!' is weaker than it looks. Because it explains its reasoning, the tool doubles as a learning aid: you can watch the rating jump as you add length, swap a common word for random ones, or break up an obvious pattern.

Under the hood the tester combines two ideas. First, it estimates entropy, the measure of unpredictability in bits, roughly from how large the character set is and how long the password is (entropy grows with length far faster than with added symbols). Second, it penalizes patterns: a long password that is really a known phrase or a keyboard walk is scored down because attackers try those guesses first. The combined score maps to a label such as Weak, Fair, Strong, or Very Strong, often alongside a rough time-to-crack figure for context.

On privacy: this tool runs entirely in your browser. Your password is never sent to our servers, logged, or stored, and nothing leaves the page. That said, treat any time-to-crack number as a ballpark, not a guarantee. Independent research has shown the same password can be rated wildly differently across tools (in one study, estimates for one password ranged from about a minute to billions of years), because results depend on the attacker model assumed. Use the rating to compare options and catch obvious weaknesses, not as proof a password is unbreakable.

Frequently asked questions

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

Yes. The check runs locally in your browser using JavaScript, so the password is never transmitted to a server, logged, or saved. As a habit, though, it is best to test the kind of password you plan to use rather than one already protecting a live account.

Why is my long password still rated weak?

Length alone is not enough if the password is predictable. A long string that is a dictionary word, a name, a date, a keyboard pattern like 'qwertyuiop', or a common phrase gets penalized because attackers guess those first. Mix unrelated words or random characters to raise the score.

How accurate is the time-to-crack estimate?

Treat it as a rough comparison, not a promise. The figure depends on assumptions about the attacker's hardware and method, so different tools can disagree by orders of magnitude for the same password. Use it to tell weak passwords from strong ones, not to declare a password uncrackable.

What does password entropy mean?

Entropy measures unpredictability in bits: each extra bit roughly doubles the number of guesses needed. As a rough guide, aim for 60 or more bits for everyday accounts and 80 or more for sensitive ones like email, banking, or a password manager master password.

Is a passphrase better than a complex short password?

Usually, yes. Current NIST guidance favors length over forced complexity and recommends allowing passphrases up to 64 characters. Four or more unrelated random words are easy to remember and hard to crack, often beating a short string of mixed symbols.

From our blog

How to Compare Two Texts and Actually Trust the Differences

By the Super Simple Digital Tools Team · Updated June 2026

Comparing two versions of a document by eye is one of those tasks that feels easy and goes wrong constantly. The human eye is excellent at reading meaning and terrible at catching a single transposed digit, a removed "not," or a clause that changed from "may" to "shall." A text diff checker removes that guesswork by mechanically aligning the two versions and coloring in every place they disagree. The skill worth learning is not how to run it, but how to read the output and how to set up your inputs so the differences it reports are the ones you care about.

Start by deciding which view fits the job. A side-by-side view is best when you want to read both versions in context, for example reviewing a rewritten paragraph or comparing two contract drafts where surrounding wording matters. A unified view stacks the changes into one column with plus and minus markers, which is denser and closer to what you would paste into a chat or commit message. Unified shines for code and config because it shows only the changed regions plus a few lines of context, so a small edit in a large file does not bury you in unchanged text.

Understanding what the tool is doing helps you trust it. Internally it solves the longest common subsequence problem: it finds the largest ordering of lines (or words) that both texts share, then everything outside that shared backbone becomes an addition or a deletion. The dominant method is Eugene Myers' 1986 algorithm, which frames the comparison as finding the shortest route through an edit graph and runs in O(ND) time, where D is the number of differences. Because git, GNU diff, and most review tools use this same family, the diff you see here is consistent with the diff your teammates see.

The most common surprise is a diff that flags things you cannot visually distinguish. This is the algorithm doing its job, not a bug. Trailing whitespace, a tab swapped for spaces, Windows versus Unix line endings, and curly versus straight quotes are all real byte-level differences. When that noise gets in the way, normalize your inputs first: strip trailing spaces, standardize line endings, or paste plain text rather than copying from a formatted editor. When precision is the whole point, such as auditing a legal change, leave them in so nothing slips past.

Finally, treat the diff as evidence, not a verdict. It tells you exactly where two texts differ, but it cannot tell you whether a change is intentional, correct, or dangerous. A diff can show that a license URL changed or that a tax rate moved from 18 to 1.8, but you still have to judge whether that edit should have happened. Used that way, with a sensible view, clean inputs, and your own review on top, a diff checker turns version comparison from a slow, error-prone chore into a fast and reliable check.

Use side-by-side for prose and contracts where context matters; switch to unified for code, config, and anything you will paste into chat or a commit.
Normalize line endings and strip trailing whitespace before diffing if you only care about real content changes, to cut out invisible noise.
Diff two JSON or API responses to instantly spot an added, removed, or renamed field instead of scanning nested objects by hand.
When verifying a revised contract or config, leave whitespace and quote differences in place so subtle but real edits are not hidden.

Read the full guide →

Tool by the Super Simple Digital Tools Team. Reviewed by our editorial team. Free to use, no signup required.