Regex Tester
Test and debug regular expressions with live matching
What is a regular expression (regex)?
A regular expression (regex or regexp) is a pattern used to match, search, and manipulate text. Regex is built into virtually every programming language and is used to validate inputs, extract data, find and replace strings, and parse structured text formats.
This tester lets you write a regex pattern and see matches highlighted in real time. It supports JavaScript regex syntax with all standard flags (global, case-insensitive, multiline, dotAll, unicode). Match results and capture groups are shown as you type.
How to use Regex Tester
Enter your regex pattern
Type your regular expression in the pattern field. JavaScript regex syntax is supported.
Set flags
Toggle flags as needed: g (global — find all matches), i (ignore case), m (multiline), s (dotAll — dot matches newlines).
Enter test text
Paste or type the text you want to match against in the test area below.
Review matches
Matches are highlighted in real time. Capture groups are shown in the match list.
Frequently asked questions
What regex flavor does this tester use?
JavaScript (ECMAScript) regex syntax. This is the same flavor used in Node.js, browser JavaScript, and most modern web frameworks. It differs slightly from PCRE (Perl-compatible) used in PHP, Python, and many other languages.
What are regex flags?
Flags modify how the pattern matches: g finds all matches (not just the first), i makes matching case-insensitive, m makes ^ and $ match line boundaries, s makes . match newlines.
What are capture groups in regex?
Capture groups are parenthesized parts of a pattern that capture the matched text for extraction. For example, (\d{4})-(\d{2})-(\d{2}) matches a date and captures year, month, and day separately.
Does my text get sent to a server?
No. All regex matching runs in your browser using the JavaScript regex engine. Your input text is never transmitted anywhere.