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Regex Tester

LiveDeveloper Utilities

Regex Tester is a free, powerful browser tool for developers who work with regular expressions daily. Write a regex pattern and instantly see matches highlighted in your test string with color-coded capture groups. Toggle flags (global, case-insensitive, multiline, dotAll, unicode), view detailed match information including group names and indices, test find-and-replace with live preview, and pick from a library of 20+ common patterns (email, URL, IP, phone, date, and more). Includes a built-in quick reference cheat sheet so you never have to leave the page. Everything runs client-side — no data leaves your browser.

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Output Summary

Export and sharing workflow optimized for web content formats.

Key Features

Real-time match highlighting as you type
Color-coded capture groups with named group support
Regex flags toggle: global, case-insensitive, multiline, dotAll, unicode
Detailed match info: full match, groups, indices, and match count
Find & Replace mode with live replacement preview
Library of 20+ common regex patterns (email, URL, IP, phone, date, etc.)
Built-in regex quick reference cheat sheet
Copy matches or replacement output to clipboard
Real-time error detection with clear messages
100% client-side — no data sent to any server
Dark mode and light mode with responsive layout

FAQs

What does the Regex Tester do?

It lets you write a regular expression pattern and test it against any text in real time. Matches are highlighted instantly with color-coded capture groups. You can also use it to test find-and-replace operations with regex.

What regex flags are supported?

The tool supports all major JavaScript regex flags: g (global — find all matches), i (case-insensitive), m (multiline — ^ and $ match line boundaries), s (dotAll — dot matches newlines), and u (unicode — full Unicode support).

Is my data safe when using this tool?

Yes. All regex processing happens 100% in your browser using the native JavaScript RegExp engine. No patterns or test strings are ever sent to a server or stored.

Does it support named capture groups?

Yes. You can use named capture groups with the (?<name>...) syntax and the tool will display group names alongside their captured values in the match details panel.

Can I use this for regex find and replace?

Yes. Switch to Replace mode, enter a replacement pattern (supports $1, $2 for group references and $<name> for named groups), and see the replaced output in real time.

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