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RegEx Tester Write, Test & Debug Regular Expressions Like a Pro

Updated on Feb 23, 2026

Stop guessing if your regex works. Our free RegEx Tester gives you live match highlighting, capture group details, and a library of common patterns — all in your browser.

RegEx Tester: Write, Test & Debug Regular Expressions Like a Pro 1

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You know that feeling when you stare at a regex pattern like ^(?=.*[A-Z])(?=.*\d)[A-Za-z\d@$!%*?&]{8,}$ and your brain just… leaves the chat? Yeah, same. Regular expressions are one of those things every developer needs to know but nobody enjoys debugging in production.

That’s why we built the RegEx Tester — a free, browser-based tool that lets you write, test, and debug regex patterns in real time. No installs, no sign-ups, no existential crises. 🎯

Why You Need a RegEx Tester (Besides Sanity)

Let’s be real: writing regex without a tester is like cooking without tasting. Sure, you can do it, but the results are unpredictable and someone’s probably going to cry.

Here’s what makes a good regex tester essential:

Instant feedback — See matches highlighted as you type, not after you deploy and break everything
Capture group visibility — Actually understand what your groups are grabbing
Flag toggling — Switch between global, case-insensitive, multiline without rewriting your pattern
Error messages that help — Know why your pattern is wrong, not just that it is

What Can You Do With It? 🔥

The RegEx Tester comes loaded with features that make regex less painful:

Live Match Highlighting

Type your pattern, paste your test string, and watch matches light up in real time. No “Run” button, no waiting — it just works. This alone saves you from the classic “did it match or didn’t it?” guessing game.

Common Patterns Library

Can’t remember the pattern for email validation? (Nobody can. It’s fine.) Just pick from the built-in library of common patterns: emails, URLs, phone numbers, IP addresses, and more. Use them as-is or as a starting point for your own.

Full Flag Support

Toggle regex flags with a click:

g (global) — Find all matches, not just the first
i (case-insensitive) — Because sometimes you don’t care about case
m (multiline) — Make ^ and $ work per line
s (dotall) — Let . match newlines too
u (unicode) — For when you’re working with emoji and international text 🌍

Capture Group Details

See exactly what each numbered and named capture group matched. This is a lifesaver when you’re building complex extraction patterns and need to know which group grabbed what.

Real-World Use Cases

Not sure when you’d use regex? Here are some everyday scenarios:

Form validation — Emails, phone numbers, passwords, postal codes
Log parsing — Extract timestamps, error codes, and IPs from server logs
Data cleaning — Strip HTML tags, normalize whitespace, fix formatting
Search & replace — Find patterns in codebases (way more powerful than Ctrl+F)
Web scraping — Extract specific data from text content

Related Tools You Might Like

If you’re working with regex, chances are you’re doing other text-wrangling too. Check these out:

Email Extractor — Pull email addresses from any text (regex under the hood!)
Phone Number Extractor — Same idea, but for phone numbers
Text Compare — Diff two strings to see what changed
Case Converter — Convert text between camelCase, snake_case, and more
HTML Stripper — Remove HTML tags from text in one click

Stop Guessing, Start Matching

Regex doesn’t have to be scary. With the right tool, it’s actually kind of… fun? (Okay, maybe “satisfying” is a better word.) Head over to the RegEx Tester and take your patterns for a spin. Your future self — the one who doesn’t have to debug regex in production at 2 AM — will thank you. 💡