Password Strength Tester
Analyze password security in real time. Get entropy scores, crack time estimates, pattern detection, and actionable improvement tips. Everything runs locally in your browser.
Requirements
Statistics
Suggestions to Improve
Generate Strong Password
How It Works
- Calculates Shannon entropy based on character pool size
- Detects sequential, repeated, and keyboard patterns
- Checks against 10,000+ common leaked passwords
- Estimates crack time assuming 10 billion guesses/second
- Generates cryptographically random passwords via Web Crypto API
Features
- Real-time analysis as you type
- Visual entropy distribution chart
- Pattern and dictionary detection
- Crack time estimation (offline attack)
- Configurable password generator
- 100% local, nothing leaves your device
What is Password Strength Tester?
Password Strength Tester is a free online tool that analyzes your passwords in real time to determine how secure they are against brute-force and dictionary attacks. It calculates Shannon entropy, detects common patterns like keyboard walks and sequential characters, checks against a database of 10,000+ leaked passwords, and estimates how long it would take to crack your password assuming 10 billion guesses per second. Everything runs entirely in your browser with zero data sent to any server.
Whether you are creating a new account password, updating old credentials, or building a password policy for your team, this tool gives you an instant, quantified assessment of password security. No signup, no upload, no tracking.
How to Use This Tool
Follow these steps to test password strength with this free online tool:
- Type or paste your password - Enter any password into the input field. Analysis begins instantly as you type, with the strength meter, entropy score, and crack time updating in real time.
- Review the strength meter - The five-segment color bar shows your password rating from Very Weak (red) through Weak, Fair, Good, to Very Strong (cyan). The estimated crack time appears beside it.
- Check requirements and statistics - The left panel shows which criteria your password meets (length, uppercase, lowercase, numbers, symbols, no repeats, not common). The right panel displays exact metrics: entropy in bits, character pool size, unique characters, detected patterns, and overall score out of 100.
- Export your results - Use the Copy Password button to grab the current password, or Export Analysis to copy a full report with all scores and metrics to your clipboard for documentation.
- Generate a strong password - Use the built-in generator to create a cryptographically random password. Configure length (8 to 128 characters), character types, and whether to exclude ambiguous characters like 0/O and 1/l. Click Copy to save it to your clipboard.
Key Features
- Real-time entropy calculation - Computes Shannon entropy based on character pool size, giving you a bits-of-entropy score that quantifies password randomness.
- Pattern and dictionary detection - Identifies keyboard patterns (qwerty, asdf), sequential characters (abc, 123), repeated sequences, leet-speak substitutions, and word+number combos that weaken passwords.
- Leaked password database check - Compares your input against 10,000+ commonly breached passwords including leet-speak variants, catching passwords like "p@ssw0rd" that seem creative but are well-known to attackers.
- Crack time estimation - Calculates how long a brute-force attack at 10 billion guesses per second would take, ranging from "Instant" to "Centuries+" depending on entropy.
- Cryptographic password generator - Uses the Web Crypto API (crypto.getRandomValues) for true randomness, with configurable length, character sets, and ambiguous character exclusion.
- Export and copy - Copy your password or export a full analysis report including all scores, requirements status, and statistics for documentation or sharing.
Common Use Cases
Security-conscious individuals use this tool before setting passwords on banking, email, and social media accounts to verify they meet modern security standards. IT administrators and developers test proposed password policies by entering sample passwords to see if their minimum requirements produce genuinely strong results. Students learning about information security use the entropy calculation and crack time estimates as a hands-on demonstration of how password length and character diversity affect security. Teams evaluating password managers use the generator to compare output quality against their existing tools.
Frequently Asked Questions
Is it safe to type my real password into this tool?
Yes. This tool runs 100% in your browser using JavaScript. Your password never leaves your device, nothing is sent to any server, and the tool works fully offline. You can verify this by disconnecting from the internet and confirming it still functions.
What does "entropy" mean for passwords?
Entropy measures the randomness (unpredictability) of your password in bits. A password with 60 bits of entropy means an attacker would need to try up to 2^60 (about 1.15 quintillion) combinations to guarantee cracking it. Higher entropy means more guesses required, which directly translates to longer crack times. Generally, 80+ bits is considered very strong for offline attacks.
How is the crack time calculated?
The tool assumes an attacker performing an offline brute-force attack at 10 billion password guesses per second (representative of a modern GPU cluster running hashcat). It divides 2^entropy by this rate to estimate the time needed. Real-world attacks may be faster with targeted dictionaries or slower against well-salted hashes with key stretching (bcrypt, Argon2).
Why does the tool flag my password as "common" even though I added numbers?
The checker performs leet-speak reversal before comparing against its leaked password database. Substitutions like @ for a, 3 for e, 0 for o, and $ for s are well-known to attackers and included in every cracking wordlist. A password like "p@ssw0rd123" is flagged because its base "password" appears in breach databases, and appending numbers is a predictable pattern attackers try first.
What makes the password generator secure?
The generator uses the Web Crypto API (crypto.getRandomValues), which provides cryptographically secure random numbers sourced from your operating system's entropy pool. Unlike Math.random(), which is predictable, Web Crypto output cannot be reproduced or guessed. Combined with configurable character sets and lengths up to 128 characters, it produces passwords suitable for high-security applications.