Regex Tester

developer

Test regular expressions against text and highlight matching patterns.

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Regex Pattern

Flags

Test Text

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What is Regex Tester?

Regex Tester is a free online developer utility. Test regular expressions against text and highlight matching patterns. It runs entirely in your browser, making it fast and accessible without any setup or installation.

How to Use Regex Tester

1
Enter your regular expression pattern in the Regex field. You can include flags like g (global), i (case-insensitive), or m (multiline).
2
Type or paste the test string in the text area below.
3
Matches are highlighted in real time as you type. The match count is shown above the text area.
4
Captured groups are displayed separately so you can verify each capture group works as expected.

Common Use Cases

→Testing email validation patterns before implementing in code.
→Debugging complex regex patterns for log parsing.
→Building and testing patterns for form input validation.
→Extracting specific data patterns from large text files.

Frequently Asked Questions

What regex flavors are supported?

This tool uses JavaScript's built-in RegExp engine, which follows the ECMAScript standard. It supports most common regex features including character classes, quantifiers, groups, lookaheads, and lookbehinds.

What do the regex flags do?

g (global) finds all matches instead of stopping at the first. i (case-insensitive) ignores letter case. m (multiline) makes ^ and $ match line boundaries. s (dotAll) makes . match newlines. u (unicode) enables full Unicode support.

How do I match a literal dot or special character?

Special regex characters (. * + ? ^ $ { } [ ] | ( ) \) must be escaped with a backslash. To match a literal dot, use \. To match a literal backslash, use \\.

What is a capture group?

A capture group is a part of the regex enclosed in parentheses ( ). It captures the matched text for that part of the pattern separately. Groups are numbered from left to right starting at 1. Named groups use the syntax (?<name>pattern).

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