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Interactive Regex Cheatsheet - Online Quick Reference

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Interactive Regex Cheatsheet

Test, learn & copy regular expressions — live matching, searchable reference, and practical examples

Live Regex Tester
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Type a regex pattern and test text to see matches highlighted here...
MATCH DETAILS
Character Classes
\d Digit
Matches any digit [0-9]
\D Non-Digit
Matches any non-digit [^0-9]
\w Word Char
Letter, digit, or underscore [A-Za-z0-9_]
\W Non-Word
Any non-word character [^A-Za-z0-9_]
\s Whitespace
Space, tab, newline, or carriage return
\S Non-Whitespace
Any non-whitespace character
. Any Character
Matches any char except newline (unless s flag)
[abc] Character Set
Matches a, b, or c
[^abc] Negated Set
Matches anything except a, b, or c
[a-z] Range
Matches any lowercase letter a through z
Quantifiers
* Zero or More
Greedy: matches 0+ occurrences
+ One or More
Greedy: matches 1+ occurrences
? Zero or One
Greedy: matches 0 or 1 occurrence
{n} Exactly n
Matches exactly n occurrences
{n,} n or More
Matches at least n occurrences
{n,m} Between n & m
Matches between n and m occurrences
*? Lazy Star
Non-greedy: matches as few as possible
+? Lazy Plus
Non-greedy one or more
Anchors & Boundaries
^ Start of String
Anchors to beginning of string/line
$ End of String
Anchors to end of string/line
\b Word Boundary
Matches at word edge (between \w and \W)
\B Non-Boundary
Matches where \b does not match
\A Absolute Start
Start of string (ignores m flag)
\z Absolute End
Absolute end of string
Groups & Lookaround
(…) Capturing Group
Captures matched content; accessible via \1, $1
(?:…) Non-Capturing
Groups without capturing; better performance
(?=…) Pos. Lookahead
Asserts what follows matches pattern
(?!…) Neg. Lookahead
Asserts what follows does NOT match
(?<=…) Pos. Lookbehind
Asserts what precedes matches pattern
(? Neg. Lookbehind
Asserts what precedes does NOT match
| Alternation
Logical OR: matches left or right pattern
\1 Backreference
References 1st captured group content
Escape Sequences
\n Newline
Line feed character (LF)
\t Tab
Horizontal tab character
\r Carriage Return
Carriage return character (CR)
\\ Backslash
Literal backslash character
\. Literal Dot
Matches a literal period character
\* Literal Asterisk
Matches a literal * character
\+ Literal Plus
Matches a literal + character
\x{…} Hex/Unicode
Matches char by hex or Unicode codepoint
Common Shorthands
[0-9]+ Digits Only
One or more numeric digits
[A-Za-z]+ Letters Only
One or more alphabetic characters
[A-Za-z0-9]+ Alphanumeric
Letters and digits combined
#[0-9A-Fa-f]{6} Hex Color
Matches 6-digit hex color codes
\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3} IPv4 (Simple)
Basic IPv4 address pattern
Common Regex Examples — Click to Try
Email
user@domain.com
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URL
https://...
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Phone
+1-555-123-4567
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Date (YYYY-MM-DD)
2024-01-15
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Hex Color
#ff5733
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SSN (US)
123-45-6789
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Frequently Asked Questions
A regular expression (regex) is a sequence of characters that defines a search pattern. It is used for string matching, validation, extraction, and replacement in text processing. Regex engines interpret special metacharacters (like ., *, +, [], ()) to create flexible and powerful search patterns. Regex is supported in virtually all programming languages including JavaScript, Python, Java, PHP, and .NET.
Greedy quantifiers (*, +, ?, {n,m}) match as many characters as possible while still allowing the overall pattern to succeed. Lazy quantifiers (*?, +?, ??, {n,m}?) match as few characters as possible. For example, given the string "<div>hello</div>", the greedy pattern <.*> matches the entire string, while the lazy pattern <.*?> matches just "<div>".
To match special regex metacharacters literally, you must escape them with a backslash \. Common metacharacters that need escaping include: ., *, +, ?, ^, $, {, }, (, ), [, ], |, /, and \. For example, to match a literal period, use \.. Inside a character class [], most metacharacters lose their special meaning and don't need escaping.
Lookahead (?=…) and lookbehind (?<=…) are zero-width assertions that check if a pattern exists (or doesn't exist) ahead of or behind the current position, without consuming characters. Positive lookahead (?=pattern) asserts the pattern does follow. Negative lookahead (?!pattern) asserts it does not follow. Similarly, positive lookbehind (?<=pattern) checks behind, and negative lookbehind (? checks that a pattern does not precede. These are invaluable for complex validation without including the assertion in the match.
The global flag ('g') makes the regex engine find all matches in the input string rather than stopping after the first match. Without 'g', only the first match is returned. With 'g', methods like match() return an array of all matches, and matchAll() returns an iterator over all match details including capture groups. In JavaScript, the 'g' flag also affects the behavior of exec() by maintaining a lastIndex for iterative matching.
Capturing groups (pattern) store the matched content in memory, accessible via backreferences (\1, \2) or in results arrays. Non-capturing groups (?:pattern) group patterns for logical or repetition purposes without storing the match. Non-capturing groups are more memory-efficient and should be preferred when you don't need to reference the matched content later. They also keep result arrays cleaner by not adding unnecessary capture entries.
You can test regex interactively right on this page using the Live Regex Tester at the top. Simply enter your pattern, select flags, and type or paste test text — matches are highlighted in real-time with full match details. You can also copy any pattern from the cheatsheet below directly into the tester. For more advanced debugging, tools like Regex101, RegExr, and RegexBuddy offer step-by-step explanations and visualization.
The most common flags are: g (global — find all matches), i (case-insensitive — ignore letter casing), m (multiline — ^ and $ match line starts/ends), s (dotall — . matches newline characters), u (unicode — enables full Unicode support), and y (sticky — matches only from lastIndex position). Flags vary slightly across programming languages and regex engines.
Pro Tip: Click any regex code in the cheatsheet to copy it. Use the search box to filter entries. Click example cards to auto-fill the tester. All matching happens locally in your browser — no data is sent anywhere.
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