Regex Tester: Test regular expressions

What Makes Regular Expressions Special?

Regular expressions help you find and work with text patterns. Think of them as a search tool with superpowers. Want to find every email address in a document? Or check if a password meets your rules? Regular expressions make these tasks simple.

How Our Regex Tester Works

Basic Steps

1. Type your pattern
2. Add your test text
3. Pick your flags
4. Click test
5. See results instantly

Flag Options

• g: Find all matches
• i: Ignore case
• m: Work with multiple lines
• s: Dot matches newlines
• u: Handle Unicode text

Common Uses for Regex

Text Validation

• Email addresses
• Phone numbers
• Passwords
• URLs
• Dates

Text Processing

• Find patterns
• Replace content
• Split text
• Clean data
• Format strings

Starter Patterns

Email Match

[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}

Phone Numbers

\d{3}[-.]?\d{3}[-.]?\d{4}

Web URLs

https?:\/\/[\w\-\.]+\.\w{2,5}\/?\S*

Quick Reference Guide

Basic Characters

• \d matches digits
• \w matches word characters
• \s matches spaces
• . matches any character
• ^ starts a line
• $ ends a line

Quantities

• ? means optional
• + means one or more
• * means zero or more
• {n} means exactly n
• {n,m} means n to m times

Smart Testing Tips

Write Better Patterns

• Start simple
• Test often
• Add complexity slowly
• Check edge cases
• Use the cheat sheet

Avoid Common Mistakes

• Test with real data
• Watch for special characters
• Check your flags
• Verify all matches
• Keep patterns simple

When to Use Regex

Perfect For

• Form validation
• Data cleaning
• Text search
• Pattern matching
• String formatting

Not Great For

• HTML parsing
• Complex text analysis
• Mathematical operations
• Binary data
• Nested structures

Tool Features

Easy Testing

• Live results
• Match counting
• Error checking
• Visual feedback
• Quick copying

Helper Tools

• Flag buttons
• Cheat sheet
• Error messages
• Match highlights
• Pattern syntax help

Pattern Building Steps

Start Right

1. Plan your pattern
2. Write basic match
3. Add quantifiers
4. Test with samples
5. Refine as needed

Test Well

1. Use varied data
2. Check all cases
3. Verify matches
4. Look for errors
5. Save good patterns

Pro Tips

Better Patterns

• Keep them readable
• Comment complex parts
• Test edge cases
• Save working patterns
• Share with others

Smart Testing

• Use real examples
• Check boundaries
• Verify results
• Test different flags
• Document patterns

Conclusion

Our regex tester helps you build and test patterns with confidence. Start with simple patterns, use the cheat sheet, and test thoroughly. Regular expressions become powerful tools when you understand them.

Frequently Asked Questions

Q: Why do my patterns sometimes miss matches?
A: Check your flags. The ‘g’ flag finds all matches, while without it you only get the first match.

Q: What’s the difference between + and *?
A: The + means “one or more” while * means “zero or more” of the previous character or group.

Q: How do I match special characters?
A: Use a backslash before special characters like . * + ? ^ $ [ ] { } ( ) | \ to match them literally.

Q: Can regex match overlapping patterns?
A: Standard regex engines don’t match overlapping patterns. You’ll need multiple passes for this.

Q: What’s the best way to learn regex?
A: Start with simple patterns, use our cheat sheet, and practice with real examples. Build complexity gradually.