What is a Regular Expression (Regex)?

A Regular Expression is a sequence of characters that defines a search pattern. It is used to match, search, validate, and manipulate text strings, and is supported by virtually every modern programming language.

What flags does this Regex Tester support?

Our tester supports the three most common JavaScript flags: g (global) finds all matches instead of stopping at the first, i (case-insensitive) treats uppercase and lowercase letters as equivalent, and m (multiline) makes ^ and $ match the start and end of each line.

Why is my pattern not matching anything?

Common reasons include: special characters not being escaped (use \. to match a literal dot), the test string not containing what you expect, or a missing flag (e.g., not using g for global matching, which only finds the first occurrence).

How do I match an email address with Regex?

A basic email regex is \b[\w.+-]+@[\w-]+\.[\w.]+\b. Note that truly validating all RFC 5322 email formats with Regex is extremely complex. For production use, always combine a basic regex check with server-side verification.

Is this tool safe? Is my data sent to a server?

Yes, completely safe. The entire regex testing process runs using JavaScript's native RegExp engine directly inside your browser. No data is ever sent to our servers, making it 100% private and secure.

Regex Tester | Quick Tool Kit

Online Regular Expression (Regex) Tester

Regular Expressions, commonly known as Regex, are one of the most powerful and versatile tools in any programmer's arsenal. Our free online Regex Tester allows you to write, test, and debug regular expressions in real time. Whether you are validating email addresses, extracting data from log files, or building complex search-and-replace logic, our tool provides instant visual feedback by highlighting every match directly within your test string. No need to write a script just to verify a pattern.

The tool supports the full JavaScript RegExp syntax and all standard flags including global (g), case-insensitive (i), and multiline (m). You can toggle these flags interactively with the provided switches, and see results update in real time. Our built-in Regex Cheatsheet serves as a quick reference for the most commonly used tokens and metacharacters, making it an invaluable resource for both beginners learning regex for the first time and experienced developers looking to refresh their memory.

Key Features of Our Regex Tester

Real-Time Highlighting: Every match is instantly highlighted in your test string as you type your pattern, providing the fastest possible feedback loop.
Interactive Flag Toggles: Switch between global, case-insensitive, and multiline modes with simple toggles instead of manually editing flag strings.
Built-in Cheatsheet: Clickable reference tokens that insert the pattern directly into the input field, accelerating your workflow significantly.

By using our Online Regex Tester, you agree that all testing and matching is processed under your responsibility. We strive for 100% accuracy and efficiency in our algorithms.