RegEx Tester

Regular Expression

/ /
Flags:

Test String

Match Result

0 Matches
Highlighted Preview
Highlight preview will appear here...
Capture Groups
No capture groups detected

Interactive Cheat Sheet

Click tokens to insert

Character Classes

  • . any character
  • \d digit
  • \D non-digit
  • \w word char
  • \W non-word char
  • \s whitespace
  • \S non-whitespace

Anchors

  • ^ start of line
  • $ end of line
  • \b word boundary
  • \B non-word bound

Groups & Ranges

  • [abc] set (a, b, c)
  • [^abc] negated set
  • [a-z] range a to z
  • (...) capture group
  • (?:...) non-cap group
  • a|b alternation

Quantifiers

  • * 0 or more
  • + 1 or more
  • ? optional
  • {3} exactly 3
  • {2,5} between 2 and 5
  • {2,} 2 or more
Empty Input · 0 ms

About EtheLab RegEx Tester & Cheat Sheet

The **Online RegEx Tester & Debugger** is a client-side regular expression workbench designed to help you construct, test, and analyze regex matching patterns. Regular expressions are sequences of characters defining search patterns, widely used for string validation, parsing, and replacements in software engineering.

How to Test and Debug Regex:

  • Enter your matching pattern in the **Regular Expression** text input (omit wrapping forward slashes).
  • Configure matching modifiers/flags (like global, case-insensitive, multiline) using the interactive tag toggles.
  • Type or paste your source text in the **Test String** input box.
  • Matches will instantly be highlighted in the results panel. Hovering over matches details indexes and captured groups.
  • Explore captured group values in the structural sidebar breakdown list.

Interactive Cheat Sheet & Privacy Safeguards

100% Local Processing Sandbox: We prioritize your data safety. Traditional regex validation tools query backend server APIs, meaning your test inputs, passwords, or emails are transmitted over the web. EtheLab processes everything locally inside your browser sandbox. None of your inputs ever leave your local computer.

Interactive Syntax Injection: Learn regex as you build. Our built-in cheat sheet classifies common tokens (Character classes, Anchors, Quantifiers, and Groupings). Simply click any token element to append it directly into your active expression input at the exact cursor position.