HOW TO USE

How to Use Regex Tester

Step-by-step guide for the Professional Regex Tester

Quick Start (4 Steps)

1

Enter your regex pattern
Type or paste your regular expression into the main input field at the top.

2

Choose your flags
Toggle the flags you need: g (global), i (case-insensitive), m (multiline), etc.

3

Paste your test text
Enter or paste the text you want to test in the large “Test Text” area.

4

View live results
See matches highlighted in real-time, explore the matches list, and use the Replace feature.

The clean interface of Regexly — pattern on top, live highlighted results on the right.

Detailed Guide

Step 1: Writing Your Regex Pattern

Enter your regular expression in the top input field. Regexly supports all standard JavaScript regex syntax.

Tip: You don’t need to wrap the pattern in forward slashes (/…/). Just type the pattern directly.

Step 2: Selecting Flags

Regexly supports these common flags:

g — Global
Find all matches, not just the first one.

i — Case Insensitive
Match both uppercase and lowercase letters.

m — Multiline
^ and $ match start/end of each line.

s — Dotall
Dot (.) matches newline characters too.

Step 3: Testing Your Text

Paste the text you want to test in the large text area. Regexly updates the results instantly as you type.

You can also click the Sample button to load example text with emails, URLs, and phone numbers.

Step 4: Understanding the Results

• Highlighted Text — All matches are highlighted in green.
• Matches List — See every match with its position and capture groups.
• Match Count — The badge shows how many matches were found.

Using the Replace Feature

The Replace section lets you transform text using your regex:

1. Enter your regex pattern
2. Type the replacement text (use $1, $2 for groups)
3. Click Replace
4. Copy the result using the copy button

Quick Presets

Regexly includes 8 ready-to-use patterns:

• Email — Extract email addresses
• URL — Find web addresses
• Phone — Match phone numbers
• Date — YYYY-MM-DD format
• IPv4 — IP addresses
• Hex Color — #RRGGBB or #RGB
• Credit Card — Basic card number pattern
• Words — Extract all words

Quick Presets make common regex tasks instant.

Best Practices

• Start simple — test small patterns before making them complex
• Use the g flag when you want to find all occurrences
• Enable i for case-insensitive matching in most real-world cases
• Use capture groups (...) when you need to extract specific parts
• Test edge cases (empty strings, special characters, very long text)
• Use the Explain button to understand complex patterns
• Always escape special characters when searching for literal text

Common Use Cases

Use Case	Recommended Pattern
Validate Email	Email preset + i
Extract URLs from text	URL preset + g
Find all phone numbers	Phone preset + g
Extract dates	Date preset + g
Find hex colors in CSS	Hex preset + gi
Clean text (remove special chars)	Use replace with [^a-zA-Z0-9\s]
Parse log files	Complex pattern with groups + gm

Troubleshooting

• Regex turns red? → You have a syntax error. Check for missing brackets, unescaped characters, or invalid quantifiers.
• No matches appearing? → Try adding the g flag or check if your pattern is too specific.
• Too many matches? → The pattern might be too broad. Add word boundaries \b or make it more specific.
• Groups not showing? → Make sure you’re using parentheses (...) around the parts you want to capture.
• Replace not working? → Use $1, $2 etc. to reference capture groups in the replacement text.
• Performance issues? → Avoid catastrophic backtracking patterns (very complex nested quantifiers).

Frequently Asked Questions

Is Regexly free?
Yes. Regexly is completely free with no limits or sign-up required.

Is my data private?
100% private. All regex processing happens directly in your browser. Nothing is ever sent to a server.

Can I use it offline?
Yes. Once the page loads, Regexly works completely offline.

What regex flavor does Regexly use?
It uses JavaScript (ECMAScript) regular expressions, the same as modern browsers.

Why aren’t my matches highlighted?
Make sure your pattern is valid and try enabling the g flag for multiple matches.

Can I test very large text?
Yes. Regexly handles large inputs efficiently, though extremely long texts may slow down complex patterns.

How do I use capture groups in replace?
Use $1 for the first group, $2 for the second, and so on.

How Regexly Finally Made Regex Testing Actually Enjoyable

For years, regex was pure pain. Then I built the tool I always wished existed.

By Rehmat Ali • Founder at Toolspool

I used to dread regex.

Not in the “this is tricky” kind of way. I’m talking full-on anxiety. Every time I needed to validate an email, extract phone numbers, or parse some messy log file, my stomach would drop a little.

I would open up some old regex I wrote six months ago, stare at it for ten minutes trying to remember what it even did, then spend the next hour testing it with random online tools that felt half-broken.

Half the time the tester would break on special characters. The other half the highlighting was terrible. And don’t even get me started on capture groups — most free tools made them almost impossible to understand.

The Moment I Finally Snapped

It was during a late-night debugging session for a client project. I had to pull every valid email from a giant CSV of user data. Simple task, right?

Except the regex I wrote kept missing edge cases. I tried three different online testers. One of them crashed the browser tab. Another one didn’t support the global flag properly. The third one had ads that kept popping up over the test area.

I spent almost two hours on something that should have taken fifteen minutes.

At 2:17 AM I closed all the tabs and thought: “I’m just going to build the regex tool I actually want to use.”

My regex workflow used to look like this:

BEFORE

• Open random regex tester
• Paste pattern
• Paste text
• Get confused by terrible highlighting
• Try different flags manually
• Give up and write a script instead

AFTER (with Regexly)

• Open Regexly
• Paste pattern
• Paste text
• See beautiful live highlighting
• Toggle flags instantly
• Done in under a minute

Introducing Regexly

Regexly is the regex tester I wish had existed five years ago.

It’s fast. It’s beautiful. It’s private. And most importantly — it actually helps you understand what your regex is doing.

No sign-ups. No uploads. Everything runs directly in your browser. Your patterns and test data never leave your computer.

What Makes Regexly Different

Here’s what I built into it based on everything that used to frustrate me:

• Instant live highlighting — Matches light up in real time as you type
• Proper group visualization — Capture groups are clearly shown with numbers
• One-click flags — g, i, m, s, u — toggle them without thinking
• Smart replace — Use $1, $2 etc. and see the result immediately
• Quick presets — Common patterns (email, URL, phone, hex, etc.) ready to use
• Clear explanations — One button that breaks down what your pattern actually does

My favorite part: The highlighted output. It feels almost magical when you finally see your complex pattern working perfectly with color-coded matches.

How I Actually Use It Every Day

Here’s my real workflow now:

1. Quick Validation

Need to check if something is a valid email or phone number? I paste the preset, type the value, and I’m done in 8 seconds.

2. Log File Parsing

When I need to extract data from server logs, I build the pattern step by step while watching the highlights update live. It’s dramatically faster than guessing.

3. Data Cleaning

I regularly use the replace feature to clean up messy data. Being able to test the replacement with $1 and $2 groups before applying it has saved me from so many mistakes.

4. Teaching & Debugging

When I’m helping someone on the team understand a regex, I just share my screen with Regexly open. The visual feedback makes explanations so much easier.

Why Privacy Actually Matters Here

I test regex on all kinds of data — customer emails, internal logs, sometimes even sensitive strings from production. I would never feel comfortable pasting that into random websites.

That’s why Regexly is 100% client-side. Once the page loads, it works completely offline. Your regex patterns and test data stay on your machine.

“I used to avoid writing regex whenever possible. Now I actually enjoy it. That’s how much better the experience is.”

Real Results

Before Regexly, regex tasks easily ate up 30–60 minutes of my week. Sometimes more when things got complicated.

Now? Most regex work takes under 5 minutes. I’ve probably saved 15–20 hours already in the last few months.

More importantly, I make fewer mistakes. The live feedback and clear group visualization means I catch issues much earlier.

Who Regexly Is Perfect For

While I originally built this for myself, it’s turned out to be useful for a lot of different people:

• Developers who work with data parsing and validation
• Data analysts who clean messy datasets
• QA engineers who write test patterns
• Students learning regular expressions
• Anyone who has ever stared at a regex for 20 minutes wondering why it’s not working

A Few Tips From Heavy Use

After using Regexly almost every day, here are the habits that help me the most:

• Always start with the g flag on unless you specifically want only the first match
• Use the presets as starting points, then tweak them
• Click the Explain button when a pattern gets complicated
• Test edge cases — empty strings, very long text, special characters
• Use the replace feature even when you’re just testing — it helps you think about the output

Pro move: Keep Regexly open in a tab. The moment you need to test something, it’s already there.

Try It Right Now

Regexly is completely free and always will be. No account. No limits. No tracking.

If regex has ever felt painful or confusing to you, give it a shot. I genuinely believe it will change how you feel about regular expressions.