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.
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.