RegEx Tester & Debugger

Test and debug regular expressions in real-time. Native JavaScript engine support with visual highlighting.

Regular Expression
/
/g
Test String
Matches (0)

No matches found with current pattern.

Understanding the RegEx Tester

Regular Expressions (RegEx) are powerful tools for pattern matching and text manipulation, but they are notoriously difficult to get right without testing. Our RegEx Tester provides a real-time sandbox where you can write patterns and see them match against your sample text instantly. It's an essential tool for developers building validation logic, scrapers, or complex search-and-replace features.

How to Use This Tool

  • 1Enter your Regular Expression pattern into the top input field.
  • 2Add any necessary flags (like 'g' for global or 'i' for case-insensitive).
  • 3Paste the sample text you want to test against in the large text area.
  • 4Watch as the matches are highlighted in real-time as you type.

Key Benefits & Features

Real-time Highlighting

See your pattern matches instantly as you modify the expression.

Full JS Engine Support

Uses the native browser JavaScript RegExp engine for 100% accurate results.

Visual Debugging

Helps you understand complex patterns like lookaheads and capture groups.

Frequently Asked Questions

What is a RegEx Tester?

A RegEx Tester is a tool that allows you to input a regular expression pattern and test it against a sample text to see if it matches correctly in real-time.

How do I use the flags (g, i, m)?

'g' stands for global (finds all matches), 'i' for case-insensitive, and 'm' for multiline. You can combine them (e.g., 'gi') to modify the search behavior.

Does this tool explain the RegEx pattern?

Yes, we provide a cheat sheet for common patterns, and our real-time matching helps you visualize how the pattern interacts with the text.

Is it safe to test sensitive data here?

Yes, all RegEx processing is done locally in your browser. Your test strings and patterns are never sent to our servers.

What happens if my RegEx is invalid?

Our tool will display a clear error message from the JavaScript RegEx engine, helping you identify and fix the syntax issue.

Can I test lookarounds and backreferences?

Yes, our tester uses the native JavaScript RegExp engine, so it supports all features available in modern browsers, including lookaheads and lookbehinds.

How do I capture groups?

Use parentheses '( )' to define capture groups. Our tool will highlight the full matches, and we are working on a feature to show individual group results.

Why is my RegEx not matching anything?

Double-check your flags and escaping. For example, if you want to match a literal dot, you must escape it like '\.'.

Is there a limit to the test text length?

While there's no hard limit, very large text blocks might slow down real-time matching. It's best used with representative samples.

Can I save my RegEx patterns?

We currently don't offer account-based saving, but you can copy the final RegEx URL (coming soon) or just copy the pattern to your clipboard.

100% Free Forever
No Data Stored
Instant Processing