Online Regex Tester

What is a Regular Expression (Regex)?

A Regular Expression (often abbreviated as Regex or Regexp) is a sequence of characters that specifies a search pattern in text. Usually, such patterns are used by string-searching algorithms for "find" or "find and replace" operations on strings, or for input validation.

Why Use an Online Regex Tester?

Writing regular expressions can be incredibly difficult, even for senior developers. The syntax is dense and heavily symbolic. A Regex Tester helps you visually debug your pattern. By typing your expression and observing real-time highlights on your test string, you can iterate and fix errors instantly without needing to compile code or run scripts.

Common Regex Flags

• g (Global): Don't return after the first match. Keep searching the entire string for all matches.
• i (Case Insensitive): Match both upper and lowercase letters identically.
• m (Multiline): Treat beginning (^) and end ($) characters as working across multiple lines, instead of just the whole string.

Basic Regex Cheatsheet