Which regex flavor is supported?

The tool uses your browser's JavaScript RegExp engine, which covers the patterns most developers use day to day.

What flags can I use?

Global (g), case-insensitive (i), multiline (m), dotAll (s) and unicode (u) are all supported via toggle buttons.

Can I see capture groups?

Yes. When your pattern contains groups, each match lists its captured values so you can verify extraction logic.

Is my test text uploaded?

No. Matching happens entirely in your browser, so your input — even sensitive sample data — stays private.

Why does my regex show an error?

If a pattern is invalid, the tool shows the error from the regex engine so you can correct the syntax.

Is there a size limit?

There is no fixed limit — performance depends on your browser, the pattern and the length of the test text.

Regex Tester Online Free

Regex Tester lets you build and debug regular expressions against your own sample text, live. Type a pattern, choose your flags (global, case-insensitive, multiline), and instantly see every match highlighted with its position and capture groups. It's the fastest way to fine-tune a pattern for validation, search or extraction before dropping it into your code. All processing happens locally in your browser, so your test data never leaves your device.

Regular expression

//g

Test text

Matches preview

Highlighted matches appear here

0 matches

How to use Regex Tester

1
Enter your regex
Type your pattern and toggle any flags you need (global, case-insensitive, multiline).
2
Add test text
Paste the text you want to match against into the test area.
3
Review the matches
Matches are highlighted live, with capture groups and counts shown below.

Why use this tool

Live match highlighting as you type
Support for common flags: g, i, m, s, u
See capture groups and match positions
Private — input never leaves your browser
Free, no sign-up

Frequently asked questions

Which regex flavor is supported?: The tool uses your browser's JavaScript RegExp engine, which covers the patterns most developers use day to day.
What flags can I use?: Global (g), case-insensitive (i), multiline (m), dotAll (s) and unicode (u) are all supported via toggle buttons.
Can I see capture groups?: Yes. When your pattern contains groups, each match lists its captured values so you can verify extraction logic.
Is my test text uploaded?: No. Matching happens entirely in your browser, so your input — even sensitive sample data — stays private.
Why does my regex show an error?: If a pattern is invalid, the tool shows the error from the regex engine so you can correct the syntax.
Is there a size limit?: There is no fixed limit — performance depends on your browser, the pattern and the length of the test text.