💪 Password Strength Checker
Test any password strength instantly. See entropy, crack time, and security tips. 100% private, no signup required.
- Create a unique password with at least 12 characters
What is a Password Strength Checker?
A password strength checker measures how resistant a password is to brute-force attacks by analysing its length, character variety, entropy, and whether it appears in known breach databases. This password strength checker calculates entropy in bits — the higher the entropy, the longer it would take to crack the password by exhaustive search. A password strength checker is an essential tool for anyone creating accounts on sensitive platforms like banking, email, or cloud storage.
How to Use This Password Strength Checker
Type or paste your password into the input field. This password strength checker analyses it instantly and shows your strength rating, entropy in bits, estimated crack time, and which character classes are present. The show/hide toggle lets you see what you are typing without clearing the field. Nothing you enter is sent to any server — this password strength checker runs entirely in your browser using JavaScript, with zero network requests.
Password Strength Checker for Security Audits
Security teams use a password strength checker to audit password policies and educate users about what makes a password strong. This password strength checker flags passwords found in the top 100 most-used password lists — these fail immediately regardless of other complexity metrics. Organisations enforcing password policies can use a password strength checker to demonstrate why length matters more than complexity: a 16-character all-lowercase passphrase outscores a short complex password.
Understanding Entropy and Time to Crack
Entropy measures uncertainty in bits. This password strength checker calculates entropy as log₂(charset size) × length, where charset size is the number of possible character types used. A password using all four character classes has an effective charset of 94 characters, making each additional character multiply security by log₂(94) ≈ 6.5 bits. The crack time estimate assumes a modern GPU performing one billion guesses per second — realistic for offline attacks against leaked hash databases.
What Makes a Password Strong?
Length is the single most impactful factor — every additional character exponentially increases crack time. This password strength checker rewards passwords over 12 characters significantly. Character variety matters too: mixing uppercase, lowercase, numbers and symbols expands the charset size. Avoid dictionary words, names, dates, and keyboard patterns. A strong password looks random. Use this free password strength checker before finalising any password for a sensitive account.
- Use at least 12 characters — length beats complexity every time
- Include all four character types: upper, lower, numbers, symbols
- Avoid common passwords like "password123" or keyboard patterns
- Passphrases (four random words) score highly on this password strength checker
- Never reuse passwords across multiple accounts
Frequently Asked Questions
What is a password strength checker?
A password strength checker measures how resistant a password is to brute-force attacks by analyzing its length, character variety, entropy, and whether it appears in known breach databases.
How does this password strength checker work?
This password strength checker analyzes your password entirely in your browser using Web Crypto API. It calculates entropy in bits, estimates crack time assuming one billion guesses per second, checks character types, and compares against a list of common passwords. Nothing is sent to any server.
Is my password safe to enter in this password strength checker?
100% safe. This password strength checker runs entirely in your browser using JavaScript. Your password never leaves your device and is never sent to any server. When you close the tab, the password is deleted from memory.
What entropy score is strong?
In this password strength checker, 60+ bits of entropy is considered good, 80+ bits is very strong. Each additional character adds approximately 6.5 bits of entropy when using all character types. Length is exponentially more important than complexity.
Why does length matter more than complexity?
Entropy grows exponentially with length but only linearly with character variety. A 16-character all-lowercase passphrase has more entropy than a short 8-character password with symbols. This password strength checker rewards length because crack time depends on charset size raised to the password length power.
Is this password strength checker free?
Yes, completely free. This password strength checker requires no signup, no account, no payment. Use it unlimited times for any number of passwords. It is a 100% free security tool.