Password Strength Checker

Analyze password strength in real time — entropy calculation, crack time estimate, and improvement suggestions.

About Password Strength Analysis

Password strength is determined by entropy — the number of bits of randomness in the password. A password with higher entropy takes exponentially longer to crack by brute force. Entropy depends on both the length of the password and the size of the character set used: using lowercase only gives 26 possibilities per character (4.7 bits), while using all printable ASCII gives 95 possibilities (6.5 bits).

This analyzer calculates entropy, estimates crack time against modern hardware (assuming 100 billion guesses per second — the approximate rate of a high-end GPU cluster doing offline hash cracking), detects common patterns like dictionary words, keyboard walks, dates, and repeated characters that reduce effective entropy, and provides specific suggestions to improve the password.

Note: This tool runs entirely in your browser. Your password is never transmitted anywhere.

FAQ

What makes a password strong?
Length matters more than complexity. A 20-character lowercase passphrase is stronger than an 8-character mixed-case password with symbols. The most important factors in order: length, avoiding common words/patterns, using varied character types, and being unique (not reused from other accounts).
What is password entropy?
Entropy measures unpredictability in bits. Each bit of entropy doubles the number of guesses needed. A password with 50 bits of entropy requires 2^50 (~1 quadrillion) guesses. At 100 billion guesses/second, that is about 3 hours. At 80 bits, it would take 380 years. At 100 bits: 400 million years.

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