Regex Tester

Test and debug regular expressions with live match highlighting — see exactly what your pattern matches in real time as you type.

What Does This Tool Do?

Regular expressions (regex) are powerful text patterns used in programming to find, match, and manipulate text. Writing them correctly can be tricky. This tool lets you type a regex pattern and see immediately which parts of your test text it matches — highlighted in real time. No more guessing whether your pattern works.

Key Features

🔍

Live Highlighting

Matching text is highlighted in real time as you type your pattern.

🚩

Flag Support

Toggle global (g), case-insensitive (i), and multiline (m) flags.

🔢

Match Count

Shows exactly how many matches were found.

⚠️

Error Display

Invalid patterns show a helpful error message instead of crashing.

How to Use This Tool

Enter your regex pattern in the pattern field.
Set the flags you want (g for all matches, i for case-insensitive, m for multiline).
Paste your test text in the left panel.
Matches are highlighted in the right panel in real time — no clicking needed.

How It Works

The pattern and flags are compiled into a JavaScript RegExp object. The test text is then scanned using the regex and each match is wrapped in a highlight span. Invalid patterns are caught and shown as error messages instead of throwing uncaught exceptions.

Common Use Cases

💡 Development & Debugging

Test regex patterns for form validation, URL parsing, log analysis, or data extraction code.

💡 Data Extraction

Build and test patterns for extracting specific data from text before using them in code.

💡 Learning Regex

Practice regex syntax and immediately see whether your pattern works as intended.

💡 Text Processing

Find and verify complex patterns in text before applying search-and-replace operations.

Frequently Asked Questions

What regex syntax is supported?

This tester uses JavaScript regex syntax, which supports character classes [a-z], quantifiers (+,*,?,{n,m}), anchors (^,$), groups (()), lookahead/lookbehind, and all standard ECMAScript regex features.

What does the "g" flag do?

The global flag (g) makes the regex find ALL matches in the text. Without it, the regex stops after finding the first match.

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