Password Strength Tester
Check how long it would take to crack your password with a brute-force attack.
Enter a password to test
Type or paste any password above to see entropy, estimated crack time, and a 0–100 strength score.
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How secure is your password? A password strength tester gives you a data-driven answer by analyzing exactly how hard your password would be to crack. Unlike vague "weak / medium / strong" labels you see on sign-up forms, this tool shows you the real numbers: entropy bits, character set size, and a precise time estimate for a brute-force attack. Whether you're checking a password you already use or testing a candidate before saving it, the password checker runs entirely in your browser — nothing is sent to any server.
What Is a Password Strength Tester?
A password strength tester (or password checker) is a tool that evaluates how resistant a password is to guessing and cracking attempts. It analyzes the composition of your password — length, character variety, and pattern complexity — and calculates the entropy, a cryptographic measure of unpredictability measured in bits. Higher entropy means exponentially more guesses are needed to crack it. This tool also translates entropy into real-world terms: how long it would take a standard brute-force attack running at one trillion guesses per second to find your exact password.
How to Use the Password Strength Checker
- Type or paste a password into the input field above. The analysis updates in real time as you type.
- Review the crack time — see how long a brute-force attack would take, from milliseconds to millennia.
- Check the score — a 0–100 rating with color-coded feedback (Very Weak → Very Strong).
- Inspect the details — view password length, entropy bits, character set size, and which character types are present.
- Improve your password — add length and character variety to increase the score. Aim for 80+ for sensitive accounts.
Key Features
- Real-Time Analysis
Results update instantly as you type — no button clicking needed.
- Entropy Calculation
Uses standard cryptographic entropy formula:
length × log₂(pool). - Crack Time Estimate
See human-readable time — from milliseconds to millennia — based on 1 trillion guesses per second.
- Character Set Detection
Automatically detects uppercase, lowercase, digits, and symbols in your password.
- 0–100 Score
Clear, color-coded score from Very Weak (red) to Very Strong (green).
- 100% Private
All analysis runs locally. Your password never leaves your device — zero server requests.
Understanding Entropy & Crack Time
Entropy is measured in bits and represents the number of binary guesses needed to find your password. Each additional bit doubles the difficulty. A password with 40 bits of entropy requires about 1 trillion guesses — a determined attacker with consumer hardware could crack it in seconds. A password with 80 bits of entropy requires about 1.2 quintillion guesses — that's thousands of years at one trillion guesses per second.
The character set size (pool) is determined by which types of characters appear in your password: 26 for lowercase only, 52 for mixed case, 62 with digits, and 95 with symbols. Longer passwords using a larger character set produce exponentially higher entropy.
Important caveat: This tool measures resistance to brute-force attacks only. If your password is a common word, phrase, or has been exposed in a data breach, it can be cracked almost instantly via a dictionary attack regardless of length. Always use a password generator to create random passwords.