Regex Tester: Test Regular Expressions Online with Real-Time Matching

Regular expressions are powerful — and famously tricky to get right. A regex tester lets you build, test, and debug patterns in real time before adding them to your code.

Use the MetisTools free regex tester to write and validate regular expressions interactively.

What Are Regular Expressions?

Regular expressions (regex) are patterns used to match, search, and manipulate text. They’re supported in virtually every programming language and are essential for:

• Form validation — email, phone, URL, password patterns
• Data extraction — scrape specific data from logs or documents
• Search & replace — find and transform text patterns
• Input sanitization — remove or escape dangerous characters
• Code refactoring — find and replace across files

Regex Basics: A Quick Reference

Pattern	Matches	Example
.	Any single character	h.t matches “hat”, “hot”
*	Zero or more	a* matches "", “a”, “aaa”
+	One or more	a+ matches “a”, “aaa”
?	Zero or one	colou?r matches “color”, “colour”
\d	Any digit	\d+ matches “123”
\w	Word character	\w+ matches “hello_123”
\s	Whitespace	a\sb matches “a b”
[abc]	Character class	[aeiou] matches any vowel
^	Start of string	^Hello matches “Hello world”
$	End of string	world$ matches “Hello world”
(group)	Capturing group	(foo) captures “foo”

How to Use Our Regex Tester

1. Write your regex pattern — with syntax highlighting
2. Paste test text — the data you want to match against
3. See matches in real time — highlights update as you type
4. Toggle flags — global (g), case-insensitive (i), multiline (m)
5. Extract groups — see what each capturing group matched
6. Test replacement — try regex replace patterns

Common Regex Patterns (Copy & Paste)

Email:     ^[\w.-]+@[\w.-]+\.\w{2,}$
URL:       ^https?://[\w.-]+\.\w{2,}(/\S*)?$
Phone:     ^\+?\d{1,3}?[-.\s]?\(?\d{3}\)?[-.\s]?\d{3}[-.\s]?\d{4}$
Date (ISO): ^\d{4}-\d{2}-\d{2}$
IPv4:      ^(\d{1,3}\.){3}\d{1,3}$
Password:  ^(?=.*[a-z])(?=.*[A-Z])(?=.*\d).{8,}$

Regex Testing Tips

1. Start simple — build your pattern incrementally, testing each addition
2. Watch for catastrophic backtracking — nested quantifiers like (a+)+b can freeze your engine
3. Use non-capturing groups (?:...) when you don’t need the captured value
4. Escape special characters — . * + ? [ ] ( ) { } ^ $ | \ / need escaping with \
5. Test edge cases — empty strings, max-length input, and unexpected characters

Why Use Our Regex Tester

• Real-time highlighting — see matches as you type
• Group extraction — inspect individual capture groups
• Replace mode — test regex substitution
• Flag toggles — g, i, m flags at your fingertips
• Pattern reference — built-in common patterns
• Free and private — nothing leaves your browser

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