How to Test Regex Online

Test and debug regular expressions in real-time. Free regex tester with match highlighting, capture groups, and cheat sheet. Supports JavaScript regex syntax.

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Step-by-Step Guide

1

Enter your pattern

Type your regular expression in the pattern field. The tool supports full JavaScript regex syntax including lookaheads, lookbehinds, and named groups.

2

Add test strings

Paste one or more test strings in the input area. You can test against single lines or multi-line text blocks to validate your pattern works correctly.

3

See matches highlighted

Matching text is highlighted instantly as you type. Capture groups are color-coded so you can see exactly what each group captures.

4

Set flags and refine

Toggle regex flags: global (g), case-insensitive (i), multiline (m), dotAll (s). Refine your pattern until all expected matches are correct.

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Frequently Asked Questions

What regex syntax is supported?
The tool uses JavaScript's built-in RegExp engine, supporting all ES2022+ features including named groups (?), lookbehind (?<=), and Unicode property escapes \p{}.
Can I test regex for other languages?
Most regex basics (character classes, quantifiers, anchors) work the same across languages. Advanced features like lookbehind may differ in Python, Java, or PCRE.
Why isn't my regex matching?
Common issues: forgetting the global flag (g) for multiple matches, not escaping special characters (., *, +, ?), or missing the multiline flag (m) for ^ and $ anchors.
Related Reference

Regex Cheat Sheet

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