Regex Tester

Test regular expressions live. Matches highlighted inline, capture groups listed, replace mode built in. JavaScript engine.

Pattern

g i m s

/ /g

Test String

📝

Live Matching

Every keystroke instantly re-runs the regex and highlights matches in the test string.

🎯

Capture Groups

Named and numbered groups are listed with their values for each match.

🔄

Replace Mode

Test replacements with $1, $2 capture group references before using in code.

⚡

JS Engine

Uses the native browser JavaScript regex engine — same behaviour as your Node.js or browser code.

About the Regex Tester

The DevKit4You Regex Tester is a live regular expression playground for testing, debugging, and validating JavaScript regular expressions directly in your browser. It provides instant match highlighting, capture group inspection, replace mode testing, and real-time regex execution using the native JavaScript regex engine.

Regular expressions (Regex) are powerful pattern-matching tools used across form validation, data extraction, search functionality, input sanitization, log parsing, URL matching, email validation, and text transformation. This tool helps developers quickly experiment with regex patterns before using them in production code.

JavaScript Developers Node.js Developers Frontend Engineers Backend Developers QA Engineers Students Learning Regex API Validation Form Validation

Key Capabilities

⚡

Live Regex Matching

Every keystroke instantly re-runs the regex against your test string and highlights matches in real time — no button press needed.

🎯

Capture Group Inspection

View numbered and named capture groups with their extracted values for every match. Example: (?<name>\w+)@(?<domain>\w+\.\w+)

🔄

Replace Mode

Test replacement logic before using it in production code. Supports capture group references like $1, $2, and $&.

✂️

Split Mode

Test how a regex pattern splits strings into arrays — visualize every resulting segment before wiring it into your code.

🧩

JavaScript Regex Engine

Uses the browser's native JavaScript regex engine — matching the exact behavior of modern browsers, Node.js, and frontend frameworks.

🚩

Regex Flag Support

Toggle standard JS regex flags: g (global), i (case-insensitive), m (multiline), s (dotall) to test different matching behaviours.

📋

Quick Pattern Samples

Built-in starter examples for Email, URL, IPv4, Dates, HEX colors, and Phone numbers — load any with one click.

🚀

Fast Browser-Based Execution

All regex evaluation happens instantly in your browser with immediate visual feedback — no network round-trips.

🔒

Fully Private

No test strings or patterns are ever uploaded, stored, or logged. Everything stays on your device.

Privacy & Transparency

The DevKit4You Regex Tester is built with privacy and transparency in mind.

🔐

Local Regex Processing

All regex matching and replacements happen entirely inside your browser — nothing is sent to any server.

🚫

No Data Collection

We do not store regex patterns, save test strings, log replacements, or track any inputs.

🌐

No External APIs

The tool works completely offline without any third-party regex services or network requests.

⚡

Instant Performance

Regex execution happens locally with immediate visual feedback as you type.

🧩

Native JavaScript Behaviour

Uses the same regex engine as standard JavaScript environments, ensuring predictable results between testing and production.

How to Use

Using the DevKit4You Regex Tester is simple and fast.

01

Enter a Regex Pattern

Type your regex pattern into the pattern field between the / delimiters.
(hello|world)\s+\w+
02

Add a Test String

Enter the text you want to test against in the Test String area.
Hello World, hello devkit4you 123
03

View Live Matches

The tool instantly highlights matches, shows matching sections, and displays capture groups as you type — no button needed.
04

Inspect Capture Groups

Review extracted values from parentheses groups and named groups in the match results panel.
(\w+)@(\w+\.\w+) → $1 = username · $2 = domain.com
05

Test Replace Mode

Switch to Replace mode, enter a replacement string, and preview the output before using it in code.
Pattern: /hello/g · Replace: hi · Result: hi world
06

Test Split Mode

Switch to Split mode to see how your regex pattern divides the test string into an array of segments.
07

Toggle Regex Flags

Enable or disable g, i, m, s flags using the checkboxes next to the pattern field to test different matching behaviours.

Common Regex Examples

📧

Email Validation

/^[^\s@]+@[^\s@]+\.[^\s@]+$/

🌐

URL Matching

/https?:\/\/[^\s]+/

🌈

HEX Color

/^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})$/

📅

Date Format (YYYY-MM-DD)

/^\d{4}-\d{2}-\d{2}$/

🌍

IPv4 Address

/^(?:\d{1,3}\.){3}\d{1,3}$/

📱

Phone Number

/[+]?[(]?[0-9]{1,4}[)]?[-\s.]?[0-9]{4,9}/

Understanding Regex Basics

A quick reference for the most common regex tokens and what they match.

Token	Meaning	Example
\w	Word character — letters, digits, underscore	\w+ → "hello123"
\d	Digit — 0 through 9	\d{4} → "2026"
\s	Whitespace — space, tab, newline	\s+ → " "
.	Any character except newline (use `s` flag to include newlines)	h.t → "hat", "hit"
+	One or more of the preceding token	\d+ → "42", "007"
*	Zero or more of the preceding token	lo* → "l", "lo", "loo"
?	Zero or one — makes the preceding token optional	colou?r → "color", "colour"
( )	Capture group — extract and reference with $1, $2…	(\w+)@(\w+) → $1, $2
[ ]	Character class — match any one character inside	[aeiou] → "a", "e", "i"
^	Start of string (or line with `m` flag)	^\d → first char is digit
$	End of string (or line with `m` flag)	\d$ → last char is digit
\|	Alternation — match either left or right side	cat\|dog → "cat" or "dog"
{n,m}	Quantifier — between n and m repetitions	\d{2,4} → "12", "1234"
\b	Word boundary — position between word and non-word	\bcat\b → "cat" not "catch"