Text & String Tools

Regex Tester

Write a regular expression and see every match, capture group, and flag behavior update live as you type.

Free & unlimitedRuns in your browserNo sign-up required

Regular expression

Flags

g Globali Case insensitivem Multilines Dotall (. matches newline)

Test string

3 matches

TwoWorks is a product of TwoWorks Inc.
Frameworks like this one make developers happy.

Regular Expressions Guide

A regular expression (regex) is a sequence of characters that defines a search pattern. Regex engines are built into virtually every programming language and most developer tools.

Core regex syntax

. matches any character; \d matches digits; \w matches word characters; \s matches whitespace. Quantifiers: + (one or more), * (zero or more), ? (zero or one), {n,m} (between n and m). Anchors: ^ (start), $ (end), \b (word boundary).

Capture groups

Parentheses () create capture groups that let you extract specific portions of a match. Named groups (?<name>...) make extraction code more readable. Non-capturing groups (?:...) group without creating a back-reference.

Common flags

g (global) finds all matches; i (case-insensitive) ignores letter case; m (multiline) makes ^ and $ match line starts/ends; s (dotall) makes . match newline characters. Combine them as needed: /pattern/gi

Performance considerations

Catastrophic backtracking occurs when nested quantifiers cause exponential matching time. For example, /(a+)+$/ on "aaaaab" triggers backtracking. Always test regex against worst-case inputs, especially for user-provided patterns in server-side code.

Loading tool…

How it works

Three steps, no setup

Write your pattern

Enter a regular expression and choose which flags to apply.

Paste test text

Matches are highlighted directly in the text as you edit either field.

Inspect capture groups

Each group is listed separately with its matched value.

Common questions

Frequently asked questions

Which regex flavor does this use?

It runs on native JavaScript regular expressions, so patterns behave exactly as they would in browser or Node.js code.

Why is my match not highlighting?

Check that the global flag is enabled if you expect multiple matches — without it, only the first match is returned.

Keep exploring

Related tools

View all tools

Text & String Tools

Regex Tester

Regular Expressions Guide

Core regex syntax

Capture groups

Common flags

Performance considerations

Three steps, no setup

Write your pattern

Paste test text

Inspect capture groups

Frequently asked questions

Related tools

Text Case Converter

NATO Phonetic Alphabet Converter

Lorem Ipsum Generator

Text Analyzer

Text Comparison Tool

List Format Converter

twoworks

Regular Expressions Guide

Core regex syntax

Capture groups

Common flags

Performance considerations