Password Strength Checker
- Uppercase letters
- Lowercase letters
- Digits
- Symbols
- Consecutive characters
- Repeating pattern
- Common weak password
Check Password Security Online
What can a password strength checker detect?
Length and character types
Password length and character diversity affect the size of the possible search space. The checker measures password length and detects whether uppercase letters, lowercase letters, digits, and symbols are present, then uses these properties as part of the strength analysis.
Theoretical entropy
Theoretical entropy is estimated using password length multiplied by log2 of the character-set size. It represents theoretical complexity under the assumption that characters are selected randomly. It is not actual cracking time and does not guarantee that a password is secure. Predictable patterns can make practical security significantly lower than the theoretical value.
Sequential characters and repeated patterns
Sequences such as abc and 123, as well as repeated patterns such as aaa and abab, can be highly predictable. The checker detects sequential characters and repeated patterns separately and displays a risk warning when they are found.
Common weak passwords
Common passwords such as password, 123456, and admin may already appear in public dictionaries or commonly used password lists. If a password matches a common weak password, it should not be considered secure even when it is relatively long.
How to use the checker
Enter a password in the input field and the analysis updates in real time. The page displays a five-level strength rating, progress bar, length, character types, and theoretical entropy, followed by individual checks for uppercase letters, lowercase letters, digits, symbols, sequential characters, repeated patterns, and common weak passwords. The password input is hidden by default and can be temporarily revealed with the eye button.
Privacy
The password is analyzed only in the current browser and is not uploaded to the server or written to the URL, localStorage, sessionStorage, or cookies. Clearing the input or refreshing the page removes the current password from the page.
How does the password strength checker work?
- Analyzes passwords locally in the current browser without uploading them or writing them to the URL, localStorage, sessionStorage, or cookies
- Checks password length and uppercase, lowercase, digit, and symbol composition and provides a five-level strength rating
- Estimates theoretical entropy from password length and character-set size; it does not represent actual cracking difficulty
- Detects sequential characters and repeated patterns such as abc, 123, aaa, and abab and reports potential risks
- Checks common weak passwords such as password, 123456, and admin and clearly reports matching risks
- Updates the analysis immediately when the password changes and displays strength, entropy, and individual check results