Regex Tester - Test Regular Expressions Live

Regular Expression Tester Live

Regular Expression

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Flags: g global i ignore case m multiline s dotAll u unicode d indices

Quick patterns:

Test String

Token	Description
.	Any character except newline
\w	Word character [a-zA-Z0-9_]
\W	Non-word character
\d	Digit [0-9]
\D	Non-digit
\s	Whitespace (space, tab, newline)
\S	Non-whitespace
[abc]	Character set — a, b, or c
[^abc]	Negated set — not a, b, or c
[a-z]	Range — a through z

Token	Description
*	0 or more (greedy)
+	1 or more (greedy)
?	0 or 1 (optional)
{n}	Exactly n times
{n,}	n or more times
{n,m}	Between n and m times
*?	0 or more (lazy)
+?	1 or more (lazy)
??	0 or 1 (lazy)

Token	Description
^	Start of string / line (m flag)
$	End of string / line (m flag)
\b	Word boundary
\B	Non-word boundary
\A	Start of string
\Z	End of string

Token	Description
(abc)	Capture group
(?:abc)	Non-capturing group
(?<name>abc)	Named capture group
(?=abc)	Positive lookahead
(?!abc)	Negative lookahead
(?<=abc)	Positive lookbehind
(?<!abc)	Negative lookbehind
a\|b	Alternation — a or b
\1	Backreference to group 1

Flag	Description
g	Global — find all matches
i	Case insensitive
m	Multiline — ^ $ match line ends
s	DotAll — . matches newline
u	Unicode mode
y	Sticky — match from lastIndex
d	Generate match indices

Token	Description
\n	Newline
\r	Carriage return
\t	Tab
\0	Null character
\\	Literal backslash
\uXXXX	Unicode code point
\xHH	Hex character

What is a Regular Expression?

A regular expression (regex or regexp) is a sequence of characters that defines a search pattern. It can be used to search, match, extract, replace, and validate strings with great precision. Regex is supported in virtually every programming language and text editor, making it one of the most universally useful tools in computing.

Common Use Cases

Form validation: Verify email addresses, phone numbers, ZIP codes, credit card numbers, and URLs.
Text extraction: Pull specific data from logs, HTML, CSV, or any structured text.
Search and replace: Make complex bulk edits in code editors like VS Code or in scripts.
Log parsing: Extract timestamps, error codes, and IPs from server logs.
Data cleaning: Strip whitespace, remove duplicates, normalize formatting.

JavaScript Regex Flavour

This tool uses JavaScript's built-in RegExp object, which follows the ECMAScript regex standard. It supports most common features including lookaheads, lookbehinds, named capture groups, Unicode mode (u flag), and the d flag for match indices. Note that some features from other flavours (like PCRE's \K or .NET's balancing groups) are not available in JavaScript.