Is my test data sent to a server?

No. All regex matching happens locally in your browser using JavaScript's native RegExp engine. No data is transmitted.

Which regex flavor does this tool use?

This tool uses JavaScript's built-in RegExp engine, which supports ECMAScript regex syntax including lookaheads, lookbehinds, and named capture groups.

Regex Tester - Real-Time Pattern Matching

Test regular expressions with real-time highlighting. See matches, capture groups, and flags instantly. Free, private, client-side.

Pattern Matcher

lock Processing Locally

Regular Expression

/ /

Test String

The quick Brown Fox jumps over the Lazy Dog. Testing 123 and ABC patterns for regex matching.

Match Results

Matches will be highlighted here...

Matches

Groups

Chars Matched

Active Flags

info

About Regex Tester

Our Regex Tester is a free, client-side utility that lets you write regular expressions and instantly see matches highlighted in your test text. Because it runs entirely in your browser, you can safely test regex patterns against proprietary logs or sensitive data strings without any data leaving your machine.

Features

check Real-time match highlighting as you type
check Toggle flags: global, case-insensitive, multiline, dotAll
check Capture group extraction and display
check 100% client-side — safe for sensitive data

How to Use

Type your regular expression in the pattern field
Toggle the flags (g, i, m, s) as needed
Enter or paste your test string below
Matches are highlighted instantly in the results panel