Regex Tester for Password Rules

Test if a password meets specific complexity rules using regular expressions. Perfect for developers and users facing strict password policies.

Password to Test

Regex Pattern

Common Password Patterns

Minimum 8 characters

At least 8 characters long

^.{8,}$

Contains uppercase

At least one uppercase letter

(?=.*[A-Z])

Contains lowercase

At least one lowercase letter

(?=.*[a-z])

Contains number

At least one digit

(?=.*\d)

Contains special character

At least one special character

(?=.*[!@#$%^&*(),.?":{}|<>])

Strong password (8+ chars, mixed case, number)

Common strong password requirement

^(?=.*[a-z])(?=.*[A-Z])(?=.*\d...

Very strong password

12+ chars with all character types

^(?=.*[a-z])(?=.*[A-Z])(?=.*\d...

No consecutive repeats

No character repeated 3+ times

^(?!.*(.)\1{2,})

Regex Pattern Guide

Regular expressions (regex) are patterns used to match character combinations. Common password regex components:

(?=.*[a-z]) - Positive lookahead for lowercase
(?=.*[A-Z]) - Positive lookahead for uppercase
(?=.*\d) - Positive lookahead for digit
.{8,} - At least 8 characters
^...$ - Match entire string

How It Works

This tool tests passwords against regular expression (regex) patterns to verify they meet specific format requirements - essential for validating password policies.

The testing process:

Pattern input: Enter a regex pattern that defines your password requirements, or select from common preset patterns.
Password testing: Your password is tested against the pattern using JavaScript's RegExp engine.
Match evaluation: The tool reports whether the password matches the pattern and highlights which parts matched.
Pattern library: Pre-built patterns cover common requirements like minimum length, character types, and complexity rules.

Regex patterns use special syntax to define rules: (?=.*[a-z]) requires lowercase, .{8,} requires 8+ characters, and ^...$ ensures the entire password is checked.

When You'd Actually Use This

Password Policy Development

Test and refine regex patterns before implementing them in your application's password validation logic.

Developer Testing

Verify that your password validation regex works correctly before deploying to production.

Security Compliance Verification

Ensure passwords meet regulatory requirements (NIST, PCI-DSS) by testing against compliance patterns.

User Password Validation

Help users understand why their password was rejected by showing exactly which requirements it fails.

Pattern Learning and Education

Learn regex syntax by experimenting with different patterns and seeing how they match passwords.

Legacy System Integration

Match password requirements when integrating with systems that have specific, documented password patterns.

What to Know Before Using

Regex is powerful but can be complex

Regular expressions have a learning curve. Start with the preset patterns and modify them gradually as you understand the syntax.

Different systems use different regex flavors

JavaScript regex (used here) differs slightly from PCRE, Python, or .NET. Patterns may need adjustment when moving between platforms.

Lookahead assertions don't consume characters

Patterns like (?=.*[A-Z]) check for conditions without advancing through the string. Multiple lookaheads can be combined to require multiple conditions.

Special characters need escaping

Characters like . * + ? ^ $ ( ) [ ] { } | \ have special meaning in regex. Use \ to match them literally (e.g., \$ to match a dollar sign).

Testing doesn't guarantee security

A password can match a complex regex pattern but still be weak (like "Password1!" which meets most requirements but is commonly used).

Common Questions

What's the most common password regex pattern?

A typical strong password pattern is: ^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[!@#$%^&*]).{8,}$ - requiring lowercase, uppercase, digit, symbol, and minimum 8 characters.

How do I require at least one number?

Use (?=.*\d) as a lookahead assertion. This checks that anywhere in the password there's at least one digit without consuming any characters.

Why use ^ and $ in password patterns?

^ matches the start and $ matches the end of the string. Without them, the pattern could match just part of the password. They ensure the entire password is validated.

How do I allow only specific special characters?

Use a character class with only allowed symbols: [!@#$%^&*] matches only those specific characters. Adjust the list based on your requirements.

Can I limit maximum password length with regex?

Yes, use {8,20} instead of {8,} to require between 8 and 20 characters. However, length limits are often better enforced outside regex.

What does the ?= syntax mean?

It's a positive lookahead assertion. (?=.*[A-Z]) means "from this position, there must be zero or more characters followed by an uppercase letter somewhere ahead."

How do I test multiple patterns at once?

Test each requirement separately with individual patterns, or combine them with lookahead assertions. Multiple small patterns are often easier to debug than one complex pattern.

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