Regex Tester

Developer Tools

Test regular expressions online and see every match and capture group live — free regex tester.

Pattern

Flags

global ignore case multiline dot matches newline

Test text

This tool needs JavaScript enabled in your browser to calculate results.

About

About the Regex Tester

Runs a regular expression against sample text and lists every match, its position and its capture groups.

Developers use it to build and debug a pattern before dropping it into code, while data analysts use it to check that a pattern captures the right groups from messy text before writing a full extraction script. It's one of many free developer tools on Toolapt, and like every tool here, it's free to use with no sign-up and no limit on how many times you run it.

Guide

Using the Regex Tester

How to use 4 Features 7 Who uses this 4

1

Step 1

Type your regular expression into the Pattern field, without the surrounding slashes.
2

Step 2

Toggle the flags you need: global, ignore case, multiline, dot matches newline.
3

Step 3

Paste the text you want to test against into the Test text box.
4

Step 4

Click "Run test" to see every match, its index and its capture groups.

Uses JavaScript's native RegExp engine, so results match what your code will actually do
Toggle global, ignore-case, multiline and dot-matches-newline flags independently
Lists every match with its exact character index in the text
Shows every capture group's value for each match, numbered
Guards against catastrophic patterns by capping results at 5,000 matches
Works entirely in your browser — nothing you type is sent to a server
Free to use, with no sign-up and no limit on how many times you run it

Developers

Developers use the Regex Tester for building and debugging a pattern against real sample text before dropping it into their code.

Data analysts

Data analysts use the Regex Tester for checking that a pattern captures the right groups from messy text before writing a full extraction script.

QA engineers

QA engineers use the Regex Tester for verifying a validation pattern matches (or correctly rejects) a set of edge-case inputs.

Students learning regex

Students learning regex use the Regex Tester for seeing immediately how a pattern and each flag actually behaves against real text.

Examples

Regex Tester examples

3 worked examples

Extracting email addresses

Set Pattern to \b\w+@\w+\.\w+\b with the global flag on, paste "Contact us at info@example.com or sales@example.com", and Run test lists both addresses with their index (14 and 34) and full match.

Capturing groups from a date

Use pattern (\d{4})-(\d{2})-(\d{2}) against "2026-09-28" to get one match with three capture groups: 2026, 09 and 28.

Case-insensitive matching

Search for "hello" with the ignore case flag on against "Hello there, HELLO again" to match both — Hello at index 0 and HELLO at index 13 — despite the different capitalization.

Cron Expression Parser

List the next run times for a five-field cron schedule, in UTC.

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HTTP Status Code Lookup

Look up what an HTTP status code means, or search the full list.

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Code Beautifier

Auto-format messy JavaScript, HTML or CSS with consistent indentation.

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Syntax Highlighter

Turn a code snippet into highlighted HTML you can paste into a blog post or page.

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Regex Cheat Sheet

A searchable quick reference for common regular expression syntax.

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SQL Formatter

Break a SQL query onto multiple lines at major keywords for easier reading.

Use it

FAQ

Frequently asked questions

Quick answers to common questions about the Regex Tester.

Still have a question?

Send us a message and we'll help you out.

What does the Regex Tester do?

It runs a regular expression against sample text and lists every match, its position, and its capture group values.

Is the Regex Tester free to use?

Yes. It's free, with no sign-up, no watermark and no limit on how many times you use it.

Is my pattern and text safe when I use this tool?

Yes. Matching happens entirely in your own browser using JavaScript's built-in RegExp engine — nothing you type is sent to a server.

What do the four flags do?

Global finds every match instead of stopping at the first. Ignore case matches letters regardless of case. Multiline makes ^ and $ match the start and end of each line rather than the whole string. Dot matches newline makes the . token also match line-break characters.

Why does the tool always add the g flag internally?

It needs the g flag to step through and collect every match. If you turn "global" off, the tool still scans but stops after the first match, matching what a non-global regex would find.

What happens with a pattern that matches an empty string?

The tool automatically advances past a zero-length match so it doesn't get stuck in an infinite loop, and still reports it as a match.

Is there a limit on how many matches it will show?

Yes, it stops at 5,000 matches to keep the page responsive, and tells you if it stopped early.

Can I use the Regex Tester on my phone?

Yes. The page is fully responsive and works on mobile, tablet and desktop browsers alike.

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Regex Tester

About the Regex Tester

Using the Regex Tester