Regex Tester

Test regular expressions with live match highlighting, capture group display, and common pattern presets.

What is a Regular Expression?

A regular expression (regex or regexp) is a sequence of characters that defines a search pattern. Regular expressions are used in programming languages, text editors, and command-line tools to find, match, and manipulate text. They are essential for tasks like input validation, data extraction, search-and-replace operations, and log parsing.

This regex tester lets you write and test regular expressions against sample text in real time, with instant visual feedback showing exactly what your pattern matches.

How to Use This Regex Tester

Enter your pattern — Type your regular expression in the pattern field at the top.

Set flags — Toggle regex flags (global, case-insensitive, multiline, etc.) using the flag buttons.

Add test text — Paste or type the text you want to test against in the text area.

See matches — Matches are highlighted in real time as you type. Capture groups are displayed separately.

Use presets — Select from common regex patterns (email, URL, IP address, etc.) to get started quickly.

Common Use Cases

Input validation — Test patterns for validating emails, phone numbers, URLs, and other user inputs before using them in your code.

Data extraction — Build patterns with capture groups to extract specific pieces of information from structured text like log files or CSV data.

Search and replace — Develop and test complex find-and-replace patterns before applying them in your IDE or codebase.

Learning regex — Experiment with patterns and see instant visual feedback to build your understanding of regular expression syntax.

Frequently Asked Questions

How do I test a regex pattern?

Enter your regular expression in the pattern field and your test string in the text area below. Matches are highlighted in real time as you type. You can also view captured groups and their positions.

What regex flags are available?

This tool supports standard JavaScript regex flags: g (global), i (case-insensitive), m (multiline), s (dotAll), and u (Unicode). Toggle them using the flag buttons next to the pattern input.

What are regex capture groups?

Capture groups are portions of a regex pattern enclosed in parentheses. They let you extract specific parts of a match. This tool displays each capture group separately so you can verify your pattern extracts the right data.