Regex Tester

How to use Regex Tester

1. Enter your regular expression in the pattern box.
2. Toggle flags such as i (ignore case) or m (multiline).
3. Paste text and review the highlighted matches and group table.

Regex in one minute

A regular expression describes a pattern of text. Plain characters match themselves, and special symbols add flexibility: . matches any character, \d a digit, \w a word character, + means one or more, * zero or more, ? optional, and parentheses create groups you can capture.

Handy patterns to try

• Email (simple): [\w.+-]+@[\w-]+\.[\w.]+
• Digits only: ^\d+$
• Date like 2026-10-17: (\d{4})-(\d{2})-(\d{2})
• Hex colour: #?([0-9a-f]{3}|[0-9a-f]{6})
• Words starting with A: \bA\w*

Avoiding common traps

Greedy quantifiers match as much as they can: <.+> grabs from the first < to the last > on the line, while <.+?> stops at the first >. Nested quantifiers such as (a+)+ can cause catastrophic backtracking that freezes a page, so test patterns on realistic input before using them in production. Remember that regex is a poor fit for fully parsing HTML or complex email validation.

Learning regular expressions step by step

Start with literal text, confirm it highlights, then add one feature at a time. Anchors ^ and $ pin a match to the start and end of a line (with the m flag) or of the whole text. Character classes like [A-Z] match one character from a set. Quantifiers such as {2,4} control repetition. Groups in parentheses let you capture parts of a match, which the table below the preview lists as $1, $2 and so on.

Use the non-capturing form (?:…) when you only need grouping. Lookaheads like (?=…) check what follows without consuming it. Because this tool uses your browser’s JavaScript engine, anything that works here works in a JavaScript or TypeScript project.

Why use this regex tester tool

• Live highlighting. Matches update as you type.
• Capture groups. See each group value and its index.
• Clear errors. Syntax problems are reported immediately.

Frequently asked questions

More free tools