Regex Tester

About the Regex Tester

The Regex Tester is a powerful, real-time tool designed to help developers build, test, and debug Regular Expressions effortlessly. Whether you are validating email formats, extracting data from logs, or performing complex text replacements, this tool provides an intuitive interface to visualize your matches instantly.

Features

Live Highlighting: See exactly what your pattern matches in real-time as you type, thanks to our dual-layer syntax highlighting engine.
Match Breakdown: Every match is parsed and broken down into capturing groups and named groups, making debugging complex patterns a breeze.
One-Click Presets: Quickly load common regex patterns for Emails, URLs, IP Addresses, and more.
Client-Side Execution: All testing happens instantly in your browser. No data is sent to a server, ensuring your sensitive text strings remain completely private.

Simply type your regular expression in the top field, toggle the desired flags, and paste your text into the testing area below to see the results immediately.

Frequently Asked Questions

How do I test a regular expression online?

Enter your regular expression in the pattern input and type or paste your test text in the content area below. Our tool will evaluate the regex in real-time and highlight all matching characters or groups directly within your text.

What do regex flags (g, i, m) mean?

Flags modify how the regex searches. 'g' (global) finds all matches instead of stopping at the first one. 'i' (ignore case) makes the search case-insensitive. 'm' (multiline) causes the start (^) and end ($) anchors to match the start and end of individual lines.

Why is my regex not matching?

Common issues include forgetting to escape special characters (like periods or parentheses), using the wrong flags (like missing the 'i' flag for case-insensitive matching), or failing to account for hidden whitespace and line breaks in the test string.

Can I test regex replace/substitution here?

While this specific view is optimized for matching and highlighting extraction, you can easily verify what will be replaced by ensuring your capture groups and global flags are highlighting the exact string segments you intend to substitute.

What are common regex patterns for email or URL?

Email and URL validation patterns can be extremely complex. For general use, a simple email regex looks like `^\S+@\S+\.\S+$`. However, for production systems, it is often better to use built-in library functions rather than custom regex for standard formats.

// Regular Expression

// Test String