Which regex flavor does this tool use?

This tool uses JavaScript regex (ECMAScript 2015+), which supports: named capture groups (`(? ...)`), lookahead and lookbehind assertions, unicode property escapes (u flag), dotAll mode (s flag making `.` match newlines), and sticky mode (y flag). It does not support PCRE-specific syntax like possessive quantifiers (`++`) or atomic groups, which are only available in Perl, PHP, and Java regex.

What are regex flags?

Flags modify pattern matching behavior. `g` (global) finds all matches instead of stopping at the first. `i` (case-insensitive) makes `[a-z]` match uppercase too. `m` (multiline) makes `^` and `$` match line start/end rather than string start/end. `s` (dotAll) makes `.` match newline characters. `u` enables full Unicode support and Unicode property escapes like `\p{Letter}`.

How do I match a literal dot or special character?

Escape special characters with a backslash to match them literally. In JavaScript regex, characters requiring escaping: `. ^ $ * + ? { } [ ] ( ) | \`. For a literal dot: `\.` — without the backslash, `.` matches any character. For a literal dollar sign: `\$`. A safe approach: escape any non-alphanumeric character with `\` if you are unsure whether it has special meaning.

Can I test multi-line strings?

Yes. Paste multi-line text directly into the test string field — newlines are supported. With the `m` flag enabled, `^` matches the start of each line and `$` matches the end of each line. Without `m`, `^` and `$` match only the very start and end of the entire string. The `s` flag makes `.` match newlines, useful for matching spans that cross line breaks.

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Free Regex Tester — Live Regular Expression Match Highlighter

A regular expression (regex) is a pattern used to match, search, and extract text. This tool tests your regex pattern against a test string in real time, highlights all matches, shows capture groups, and supports all JavaScript regex flags (g, i, m, s, u). No server round-trip — results update as you type.

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How It Works

How to use Regex Tester

Enter your pattern

Type your regular expression in the Pattern field. Do not include surrounding slashes.

Add flags and test string

Select flags (g for global, i for case-insensitive, m for multiline). Paste the text you want to test against.

See live matches

Matches are highlighted in the test string. Capture groups and match positions are listed below.

FAQ

Frequently asked questions

A regular expression (regex) is a sequence of characters that defines a pattern for matching, searching, and extracting text. It is used in input validation (email, phone number formats), search-and-replace in code editors, log file parsing, URL routing in web frameworks, and data extraction from unstructured text. Regex is supported natively in almost every programming language.

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Free Regex Tester — Live Regular Expression Match Highlighter

How to use Regex Tester

Frequently asked questions

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