Password Strength Checker
What Is It?
The Password Strength Checker analyzes your password in real-time and provides a comprehensive security assessment including strength level, entropy score, character set size, estimated crack time, and specific suggestions to improve weak passwords.
Your password never leaves your browser — all analysis is performed locally using JavaScript.
How to Use
- Type your password in the input field.
- The strength meter and stats update instantly.
- Review the requirements checklist to see what’s missing.
- Read the suggestions section to understand how to improve the password.
- Toggle the eye icon to show/hide the password while typing.
Strength Levels
| Level | Description |
|---|---|
| Very Weak | Trivially guessable. Should not be used. |
| Weak | Vulnerable to common attacks. Needs improvement. |
| Fair | Adequate for low-risk accounts. Can be improved. |
| Strong | Good resistance to brute force. Recommended for most accounts. |
| Very Strong | Excellent entropy. Suitable for high-security applications. |
Understanding Entropy
Entropy measures how unpredictable your password is. It’s calculated as:
Entropy = Length × log₂(Charset Size)
Where charset size is the number of unique character categories used (lowercase, uppercase, numbers, symbols). A higher entropy means an exponentially stronger password.
| Entropy Range | Security Level |
|---|---|
| < 28 bits | Very Weak |
| 28–35 bits | Weak |
| 36–59 bits | Fair |
| 60–127 bits | Strong |
| 128+ bits | Very Strong |
Requirements Checklist
- ✓ At least 12 characters
- ✓ Uppercase letters (A-Z)
- ✓ Lowercase letters (a-z)
- ✓ Numbers (0-9)
- ✓ Special characters (!@#$%^&*)
- ✓ No repeated sequences (e.g., “aaa”)
Benefits
- Real-time feedback — no button needed, analysis updates as you type.
- Entropy scoring — scientifically accurate measurement of password randomness.
- Crack time estimate — know how long it would take a modern GPU to brute-force your password.
- Actionable suggestions — specific advice to improve weak passwords.
- Completely private — zero server involvement.
Common Use Cases
- Checking the strength of passwords before using them on critical accounts.
- Teaching users about password requirements in security training.
- Verifying that generated passwords meet security thresholds.
- Learning what makes a password strong vs. weak.
Frequently Asked Questions
How is the crack time estimated?
The estimate assumes an attacker using a modern GPU-based brute-force setup at approximately 10 billion guesses per second. The actual crack time depends on the attacker’s resources, the hashing algorithm used to store the password, and whether the password appears in common word lists.
Should I check my real passwords here?
The tool is designed to show you the principles that make passwords strong. However, for maximum security, consider using our Password Generator to generate a completely random strong password instead of testing your actual passwords.
What’s the difference between entropy and length?
Length is just one factor. A 20-character password made of only lowercase letters has fewer possible combinations than a 12-character password using all character types. Entropy accounts for both length and variety, giving a more accurate measure of strength.
