What regex flavor is supported?

We use JavaScript's regex engine, which follows ECMAScript standards and is compatible with most web applications.

Can I test replacement patterns?

Yes, you can test both matching and replacement operations with capture groups.

Are matches highlighted?

Yes, all matches are highlighted in the test string with different colors for capture groups.

Regex Tester: Live Matching & Capture Groups

The Use-It-Anywhere Regex Tester & Debugger

SimplyUtils Regex Tester is the ultimate free online tool for building, testing, and debugging Regular Expressions (Regex). Whether you're a seasoned developer scraping data or a beginner validating email forms, our tool provides a real-time, privacy-focused environment to perfect your patterns.

SimplyUtils vs. The Competition

See why developers are switching to SimplyUtils for their daily regex tasks:

Feature

SimplyUtils

Regex101

RegExr

100% Client-Side Privacy

✓

Partial

Yes

Integrated Cheatsheet Sidebar

✓

Local History (Auto-Save)

✓

Account Req.

Instant "Copy Pattern" Templates

✓

✗

No Account Required

✓

Top Features for Developers

Real-Time Highlighting: See matches instantly as you type. We highlight every match in your test string with distinct colors, so you never miss a character.
Deep Match Analysis: Expand the "Match Details" panel to see the exact index, length, and capturing groups (e.g., $1, $2) for every single match.
Substitution Playground: Don't just find—replace. Test your search-and-replace logic with our built-in substitution tool using standard $n syntax.
Pattern Library: One-click access to common patterns like Email, URL, IPv4, Date, and Hex Color. Stop rewriting the same regex over and over.
History Tracking: We automatically save your recent patterns to your browser's local storage. Did you accidentally refresh? No problem, your work is safe.
Built-in Cheatsheet: Forget the syntax? Our sidebar cheatsheet covers everything from Character Classes to Lookarounds, right where you need it.

Most Common Patterns to Copy

Jumpstart your development with these battle-tested regular expressions:

URL / Link

https?:\/\/(www\.)?[-a-zA-Z0-9@:%._\+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b

Email Address

^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$

Strong Password

^(?=.*[A-Z])(?=.*[a-z])(?=.*\d).{8,}$

Hex Color

#?([a-fA-F0-9]{6}|[a-fA-F0-9]{3})

Regex Syntax Crash Course

Regular expressions use special characters to define patterns. Here are the essentials:

. (Dot) - Any char except newline
\d - Digit (0-9)
\w - Word char (A-Za-z0-9_)
\s - Whitespace (space, tab)
* - Zero or more times
+ - One or more times
? - Optional (0 or 1)
^ - Start of string
$ - End of string
[] - Character set

Common Regex Errors & Fixes

Catastrophic Backtracking Avoid nested quantifiers like (a+)+ which can crash your browser on long strings. Use atomic groups or simple patterns.
Greedy vs. Lazy By default, .* is greedy and consumes as much as possible. Use .*? to make it lazy (stop at the first match).
Unescaped Special Characters Characters like . * + ? ( ) [ ] { } | \ ^ $ must be escaped with a backslash \ if you want to match them literally.

Your Code, Your Privacy

When you're testing regex against sensitive logs or customer data, you can't afford to paste it into a server-side tool. SimplyUtils processes everything locally in your browser. No data ever leaves your device.