Regex Tester – Free Online Regular Expression Tester

Test and debug regular expressions with real-time match highlighting. Supports all JavaScript regex flags (g, i, m, s, u).

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Features

🔍

Real-Time Highlighting

See matches highlighted in the test string instantly as you type or modify your regex.

🚩

All Flags Supported

Toggle global (g), case-insensitive (i), multiline (m), dotAll (s), and unicode (u) flags.

📊

Match Information

Shows match count, captured groups, index positions, and named groups for each match.

📝

Pattern History

Recent patterns are saved locally so you can reuse them.

🔒

Privacy First

All testing is local in your browser. No data is sent anywhere.

⚡

Syntax Highlighting

Your regex is color-coded to distinguish metacharacters, quantifiers, and character classes.

How to Use

1

Enter Your Regex

Type or paste your regular expression in the regex input field.

2

Set Flags

Toggle the flags you need: g (global), i (case-insensitive), m (multiline), s (dotAll), u (unicode).

3

Enter Test String

Type or paste the text you want to test your regex against.

4

View Matches

Matches are highlighted instantly. Click any match to see details like groups and index.

Frequently Asked Questions

What regex syntax is supported?
This tool uses JavaScript's RegExp engine, supporting the standard JavaScript regex syntax: character classes [abc], quantifiers *+?{n,m}, groups (), alternation |, anchors ^$, and escape sequences \d\w\s etc.
What is the difference between the flags?
g (global) finds all matches instead of just the first. i (case-insensitive) makes letters match both upper and lowercase. m (multiline) makes ^ and $ match line boundaries. s (dotAll) makes . match newlines. u (unicode) enables full Unicode support.
What are captured groups?
Parentheses in a regex create capture groups. For example, in(\d+), the \d+ is captured as group 1. Named groups (?<name>...) are also supported.
Why isn't my regex matching?
Check: Is your regex syntactically correct? Are you using the right flags? Remember . doesn't match newlines by default (use \s or the s flag). Try escaping special characters with \.
Is my data sent to a server?
No. All regex testing is done locally in the browser using JavaScript's native RegExp engine. Your patterns and test strings never leave your device.

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