Analyze password entropy, crack time, and check against known data breaches. Your password never leaves the browser.
All password analysis is performed locally in your browser. The breach check uses k-anonymity: only the first 5 characters of your password's SHA-1 hash are sent to Have I Been Pwned. The full hash never leaves your device.
Password strength is measured in entropy bits — the average number of guesses an attacker must try before hitting the password. This tool derives the charset size N from the character classes present (26 lowercase, 26 uppercase, 10 digits, 33 specials), then computes E = length × log₂(N). Each extra bit doubles the search space. The crack-time estimate divides 2^E by 10 billion guesses per second — an offline GPU brute-force rate — and formats the result as seconds, hours, years, or centuries. It also runs eight policy checks (length, case, digits, repeats, sequences, common-password lists) and a k-anonymity breach lookup against Have I Been Pwned.
Every character class widens the search space; entropy grows linearly with length and logarithmically with charset size.
Maya is rolling out a password manager for her team of ten and uses this tester to pick a safe master password. Every number below is what the tool actually computes.
To test password strength: type a candidate — the checker estimates entropy, offline crack time against GPU rigs, and flags patterns, dictionary words, and reuse risks without ever sending the password anywhere.
FreeToolHub Password Strength Checker is a free browser-based tool that scores password entropy and estimates crack time locally, no signup, no transmission.
Detailed password analysis: entropy, crack time and pattern detection. 100% local, free.
This tester analyzes password strength with real math rather than colored bars: it calculates entropy in bits from character space and length, estimates offline crack time against modern GPU attack rates, and runs nine quality checks covering length, character variety, repeated sequences, keyboard patterns, dictionary words, and common-password lists. Every finding comes with an actionable suggestion — not just weak, but weak because it contains a dictionary word and would gain 26 bits by adding four random characters. Analysis is entirely client-side: the password is never transmitted, logged, or stored, which is the only acceptable design for a tool of this kind.
Users auditing passwords before adopting them for important accounts — banking, email, the password manager's own master password. Teams teaching security hygiene demonstrate concretely why P@ssw0rd!1 fails nine checks despite looking compliant. Developers calibrate password policy rules against entropy reality instead of naive complexity rules that push users toward predictable patterns. Anyone choosing a master password for encrypted archives or crypto wallets gets the crack-time number that tells them what margin they actually have.
(1) Type a candidate password — analysis runs live per keystroke. (2) Entropy computes as length times the log2 of the character space actually used: a 12-character password from all four sets carries about 78 bits. (3) Crack time estimates apply realistic attack throughput — hundreds of billions of guesses per second for fast hashes — and translate bits into human-scale durations. (4) The nine checks report individually with specific fixes; the overall grade weighs the weakest factor, because attackers attack the weakest factor too.
The complexity rules everyone memorized — eight characters, upper, lower, number, symbol — came from 2003 guidance that its own author later apologized for, because they optimize for human predictability: P@ssw0rd1 satisfies every rule and falls instantly. The research-backed shift, formalized in NIST SP 800-63B, prioritizes length over composition, bans forced periodic rotation (which makes users increment Password1 to Password2), and screens new passwords against known-breach lists instead of guessing patterns. Current best practice: length 16 or a 4–6 random-word passphrase, uniqueness per site enforced by a password manager, breach checking at creation, and multi-factor authentication carrying the real security weight for important accounts. The math explains why: each additional random character multiplies the search space by 70–90×, while mandated symbols add only a small constant factor — and mostly just herd everyone toward the same leetspeak substitutions crackers scripted years ago. This tester's checks encode the modern ruleset, so strong here means strong against how attacks actually work.
Length beats complexity: 16+ random characters from mixed sets. A 12-character random password resists offline cracking far longer than an 8-character one with symbols and substitutions like P@ssw0rd, which dictionaries already contain.
A 12-character random mixed-set password takes centuries against typical GPU rigs; 8 characters falls in hours. This checker estimates crack time from character space and length without storing anything.
Yes when made of 4–6 random words — 25+ characters with memorable structure. Avoid famous quotes or lyric-derived phrases, which appear in cracking wordlists.
Credential stuffing replays breaches against other sites. A password manager plus unique passwords contains the blast radius of any single leak to that one account.
It calculates entropy (bits of randomness) based on character set size and length, then estimates crack time against offline attacks: 100 billion guesses/second (GPU cluster with hashcat) versus 10,000 guesses/second (online throttled login). A 12-character mixed-case password with symbols has ~71 bits of entropy—roughly 34,000 years at 100B guesses/second.
It flags dictionary words, keyboard patterns (qwerty, 1qaz2wsx), repeated characters, sequential numbers, and common substitutions (@ for a, 0 for o). It also checks against the top 100,000 breached passwords from HaveIBeenPwned datasets. "P@ssw0rd123" scores as weak despite meeting typical complexity rules.
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No paywalls, no signups, no data sold. Built by a solo developer who believes useful tools should be accessible to everyone.
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