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Regex Tester & Pattern Library - 40+ Prebuilt Regular Expressions

Regex Tester Regex Library

Testing regular expressions? Try the free Regex Tester at Orbit2x with live matching and syntax highlighting. Or browse 40+ prebuilt patterns for common tasks.

Quick Access

  • 🧪 Regex Tester - Live regex testing with match highlighting
  • 📚 Regex Library - 40+ ready-to-use patterns for email, URL, phone, etc.
  • 🔍 Grep Tool - Search text with regex patterns

Most Common Regex Patterns

Email Validation

# Basic email (99% cases)
^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$

# RFC 5322 compliant (more strict)
^[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$

Test online: Regex Tester

URL Validation

# HTTP/HTTPS URLs
^https?:\/\/(www\.)?[-a-zA-Z0-9@:%._\+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b([-a-zA-Z0-9()@:%_\+.~#?&//=]*)$

# URLs with optional protocol
^(https?:\/\/)?(www\.)?[-a-zA-Z0-9@:%._\+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b([-a-zA-Z0-9()@:%_\+.~#?&//=]*)$

Phone Numbers (US)

# (123) 456-7890 or 123-456-7890
^\(?([0-9]{3})\)?[-.\s]?([0-9]{3})[-.\s]?([0-9]{4})$

# International format (+1 123 456 7890)
^\+?([0-9]{1,3})\s?([0-9]{3})\s?([0-9]{3})\s?([0-9]{4})$

IP Addresses

# IPv4 (0.0.0.0 to 255.255.255.255)
^((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$

# IPv6
^(([0-9a-fA-F]{1,4}:){7}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,7}:|([0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:((:[0-9a-fA-F]{1,4}){1,6})|:((:[0-9a-fA-F]{1,4}){1,7}|:)|fe80:(:[0-9a-fA-F]{0,4}){0,4}%[0-9a-zA-Z]{1,}|::(ffff(:0{1,4}){0,1}:){0,1}((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])|([0-9a-fA-F]{1,4}:){1,4}:((25[0-5]|(2[0-4]|1{0-1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9]))$

Dates

# YYYY-MM-DD
^\d{4}-(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01])$

# DD/MM/YYYY or MM/DD/YYYY
^(0[1-9]|[12][0-9]|3[01])[\/](0[1-9]|1[0-2])[\/]\d{4}$

Credit Cards

# Visa (starts with 4)
^4[0-9]{12}(?:[0-9]{3})?$

# MasterCard (starts with 51-55 or 2221-2720)
^5[1-5][0-9]{14}$|^2(?:2(?:2[1-9]|[3-9][0-9])|[3-6][0-9][0-9]|7(?:[01][0-9]|20))[0-9]{12}$

# American Express (starts with 34 or 37)
^3[47][0-9]{13}$

Browse all patterns: Regex Library with 40+ Patterns

Using Regex in Different Languages

JavaScript

// Test if string matches pattern
const email = "user@example.com";
const emailRegex = /^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/;

if (emailRegex.test(email)) {
  console.log("✅ Valid email");
} else {
  console.log("❌ Invalid email");
}

// Extract matches
const text = "Contact us at support@example.com or sales@example.com";
const matches = text.match(/[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}/g);
console.log(matches);
// ["support@example.com", "sales@example.com"]

// Replace with regex
const cleaned = text.replace(/@example\.com/g, "@newdomain.com");

// Capture groups
const urlRegex = /^(https?):\/\/([^\/]+)(\/.*)?$/;
const url = "https://example.com/path/page";
const [, protocol, domain, path] = url.match(urlRegex);
console.log({ protocol, domain, path });
// { protocol: 'https', domain: 'example.com', path: '/path/page' }

Python

import re

# Test if string matches
email = "user@example.com"
email_regex = r'^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$'

if re.match(email_regex, email):
    print("✅ Valid email")
else:
    print("❌ Invalid email")

# Find all matches
text = "Contact us at support@example.com or sales@example.com"
matches = re.findall(r'[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}', text)
print(matches)
# ['support@example.com', 'sales@example.com']

# Replace with regex
cleaned = re.sub(r'@example\.com', '@newdomain.com', text)

# Capture groups
url_regex = r'^(https?):\/\/([^\/]+)(\/.*)?$'
url = "https://example.com/path/page"
match = re.match(url_regex, url)
if match:
    protocol, domain, path = match.groups()
    print(f"Protocol: {protocol}, Domain: {domain}, Path: {path}")

PHP

<?php
// Test if string matches
$email = "user@example.com";
$emailRegex = '/^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/';

if (preg_match($emailRegex, $email)) {
    echo "✅ Valid email\n";
} else {
    echo "❌ Invalid email\n";
}

// Find all matches
$text = "Contact us at support@example.com or sales@example.com";
preg_match_all('/[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}/', $text, $matches);
print_r($matches[0]);
// Array ( [0] => support@example.com [1] => sales@example.com )

// Replace with regex
$cleaned = preg_replace('/@example\.com/', '@newdomain.com', $text);

// Capture groups
$urlRegex = '/^(https?):\/\/([^\/]+)(\/.*)?$/';
$url = "https://example.com/path/page";
if (preg_match($urlRegex, $url, $matches)) {
    echo "Protocol: {$matches[1]}, Domain: {$matches[2]}, Path: {$matches[3]}\n";
}
?>

Go

package main

import (
    "fmt"
    "regexp"
)

func main() {
    // Test if string matches
    email := "user@example.com"
    emailRegex := regexp.MustCompile(`^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$`)

    if emailRegex.MatchString(email) {
        fmt.Println("✅ Valid email")
    } else {
        fmt.Println("❌ Invalid email")
    }

    // Find all matches
    text := "Contact us at support@example.com or sales@example.com"
    pattern := regexp.MustCompile(`[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}`)
    matches := pattern.FindAllString(text, -1)
    fmt.Println(matches)
    // [support@example.com sales@example.com]

    // Replace with regex
    cleaned := pattern.ReplaceAllString(text, "REDACTED")

    // Capture groups
    urlRegex := regexp.MustCompile(`^(https?):\/\/([^\/]+)(\/.*)?$`)
    url := "https://example.com/path/page"
    groups := urlRegex.FindStringSubmatch(url)
    if len(groups) > 0 {
        fmt.Printf("Protocol: %s, Domain: %s, Path: %s\n", groups[1], groups[2], groups[3])
    }
}

Regex Cheat Sheet

Character Classes

Pattern Matches Example
. Any character except newline a.c matches "abc", "a1c"
\d Any digit (0-9) \d{3} matches "123"
\D Any non-digit \D+ matches "abc"
\w Word character (a-z, A-Z, 0-9, _) \w+ matches "hello_123"
\W Non-word character \W+ matches "!@#"
\s Whitespace (space, tab, newline) \s+ matches " "
\S Non-whitespace \S+ matches "hello"
[abc] Any of a, b, or c [aeiou] matches vowels
[^abc] Not a, b, or c [^0-9] matches non-digits
[a-z] Range a to z [A-Z]+ matches "HELLO"

Quantifiers

Pattern Matches Example
* 0 or more a* matches "", "a", "aaa"
+ 1 or more a+ matches "a", "aaa"
? 0 or 1 colou?r matches "color", "colour"
{n} Exactly n \d{3} matches "123"
{n,} n or more \d{3,} matches "123", "1234"
{n,m} n to m \d{2,4} matches "12", "123", "1234"

Anchors

Pattern Matches Example
^ Start of string ^Hello matches "Hello world"
$ End of string world$ matches "Hello world"
\b Word boundary \bcat\b matches "cat" not "catch"
\B Non-word boundary \Bcat\B matches "concatenate"

Groups

Pattern Purpose Example
(abc) Capture group (\d{3})-(\d{4}) captures "123-4567"
(?:abc) Non-capturing group (?:https?):\/\/
(a|b) Alternation (OR) (cat|dog) matches "cat" or "dog"
(?=abc) Positive lookahead \d+(?= dollars) matches "10" in "10 dollars"
(?!abc) Negative lookahead \d+(?! dollars)

Practice with: Regex Tester

Common Regex Tasks

1. Extract Domain from Email

const email = "user@example.com";
const domain = email.match(/@(.+)$/)[1];
console.log(domain); // "example.com"

2. Validate Password Strength

# At least 8 chars, 1 uppercase, 1 lowercase, 1 number, 1 special char
^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[@$!%*?&])[A-Za-z\d@$!%*?&]{8,}$

3. Extract Hashtags

const tweet = "Learning #regex is fun! #coding #javascript";
const hashtags = tweet.match(/#\w+/g);
console.log(hashtags); // ["#regex", "#coding", "#javascript"]

4. Remove HTML Tags

const html = "<p>Hello <strong>world</strong></p>";
const text = html.replace(/<[^>]*>/g, "");
console.log(text); // "Hello world"

5. Validate Hex Color

# #RGB or #RRGGBB
^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})$

6. Extract All Numbers

const text = "I have 5 apples and 10 oranges";
const numbers = text.match(/\d+/g);
console.log(numbers); // ["5", "10"]

7. Camel Case to Snake Case

const camelCase = "myVariableName";
const snakeCase = camelCase.replace(/([A-Z])/g, "_$1").toLowerCase();
console.log(snakeCase); // "my_variable_name"

8. Validate Credit Card (Luhn Algorithm + Regex)

# Visa, MasterCard, Amex, Discover
^(?:4[0-9]{12}(?:[0-9]{3})?|5[1-5][0-9]{14}|3[47][0-9]{13}|6(?:011|5[0-9]{2})[0-9]{12})$

Regex Performance Tips

✅ DO

  1. Use specific patterns

    # ✅ Good - specific
\d{3}-\d{3}-\d{4}

# ❌ Bad - too generic
.*-.*-.*

  2. Anchor patterns

    # ✅ Good - anchored
^https?:\/\/

# ❌ Bad - searches entire string
https?:\/\/

  3. Use non-capturing groups

    # ✅ Good - non-capturing
(?:https?):\/\/

# ❌ Slower - capturing
(https?):\/\/

❌ DON'T

  1. Avoid catastrophic backtracking

    # ❌ DANGEROUS - exponential time!
(a+)+b

# ✅ Better
a+b

  2. Don't use regex for nested structures

    # ❌ BAD - Use HTML parser
<div>(.*)</div>

# ✅ Use DOMParser or cheerio instead

Tools & Resources

Online Regex Tools

Learning Resources

Regex Testing Sites

FAQ

Q: What's the difference between greedy and lazy quantifiers?

A:

  • Greedy (*, +): Match as much as possible
  • Lazy (*?, +?): Match as little as possible
const html = "<div>foo</div><div>bar</div>";

// Greedy - matches entire string
html.match(/<div>.*<\/div>/)[0];
// "<div>foo</div><div>bar</div>"

// Lazy - matches first occurrence
html.match(/<div>.*?<\/div>/)[0];
// "<div>foo</div>"

Q: How do I match newlines with .?

A: Use the s (dotall) flag:

// Without s flag - doesn't match newlines
/line1.line2/.test("line1\nline2"); // false

// With s flag - matches newlines
/line1.line2/s.test("line1\nline2"); // true

Q: What's the difference between \w and [a-zA-Z0-9_]?

A: They're equivalent in ASCII. \w also matches Unicode letters in some engines.

Q: How do I escape special characters?

A: Use backslash \:

# Match literal dot
\.

# Match literal parentheses
\(\)

# Match literal backslash
\\

Related Tools

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Regex Tester & Pattern Library - 40+ Prebuilt Regular Expressions

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