Regex Tester Online

Type a regex pattern in the pattern box and test text below it — matches are highlighted in real time as you type. The Captured Groups table shows each match with its group values. All processing runs in your browser; nothing is sent to any server.

What is a regular expression?

A regular expression (regex or regexp) is a sequence of characters that defines a search pattern. Regex is used in virtually every programming language for string searching, validation, parsing, and replacement. The JavaScript engine (ECMAScript) used here follows the same rules as new RegExp(pattern, flags) in the browser.

Regex flags

Common regex patterns

\d          Digit 0–9
\w          Word character (letter, digit, underscore)
\s          Whitespace (space, tab, newline)
\b          Word boundary
.           Any character except newline (with /s flag: including newline)
^           Start of string (with /m: start of line)
$           End of string (with /m: end of line)
*           0 or more (greedy)
+           1 or more (greedy)
?           0 or 1 (or makes * + ? lazy)
{n,m}       Between n and m times
(abc)       Capturing group
(?:abc)     Non-capturing group
[a-z]       Character class
[^a-z]      Negated character class

Email:    ^[\w.-]+@[\w.-]+\.\w{2,}$
URL:      https?://[\w./-]+
Date:     \d{4}-\d{2}-\d{2}
IPv4:     \b(?:\d{1,3}\.){3}\d{1,3}\b
Hex color: #[0-9a-fA-F]{3,6}

Code examples

const pattern = /(\w+)@(\w+\.\w+)/g;
const text = 'Contact [email protected] or [email protected]';

let match;
while ((match = pattern.exec(text)) !== null) {
  console.log(`Full: ${match[0]}, User: ${match[1]}, Domain: ${match[2]}`);
}

// Replace all emails
const redacted = text.replace(pattern, '[REDACTED]');

import re

pattern = r'(\w+)@(\w+\.\w+)'
text = 'Contact [email protected] or [email protected]'

for match in re.finditer(pattern, text):
    print(f"Full: {match.group(0)}, User: {match.group(1)}")

Frequently asked questions

Related tools