Welcome to the ultimate regex cheat sheet! This comprehensive reference guide contains all the regular expression patterns, metacharacters, and examples you need to master regex. Bookmark this page for quick access to all the essential regex information.

Basic Patterns

Literal Characters

Match characters literally:

hello          # Matches "hello"
Regex          # Matches "Regex"
123            # Matches "123"

Character Classes

Match any one character from a set:

[abc]          # Matches 'a', 'b', or 'c'
[a-z]          # Matches any lowercase letter
[A-Z]          # Matches any uppercase letter
[0-9]          # Matches any digit
[a-zA-Z0-9]    # Matches any alphanumeric character
[^abc]         # Matches any character EXCEPT 'a', 'b', or 'c'
[^0-9]         # Matches any non-digit character

Shorthand Character Classes

\d             # Any digit (same as [0-9])
\D             # Any non-digit (same as [^0-9])
\w             # Any word character (same as [a-zA-Z0-9_])
\W             # Any non-word character
\s             # Any whitespace character (space, tab, newline)
\S             # Any non-whitespace character

Metacharacters

Wildcard

.              # Matches any single character (except newline)

Anchors

^              # Start of string or line
$              # End of string or line
\b             # Word boundary
\B             # Non-word boundary

Quantifiers

*              # Zero or more occurrences
+              # One or more occurrences
?              # Zero or one occurrence
{n}            # Exactly n occurrences
{n,}           # n or more occurrences
{n,m}          # Between n and m occurrences
*?             # Zero or more (lazy/non-greedy)
+?             # One or more (lazy)
??             # Zero or one (lazy)
{n,}?          # n or more (lazy)
{n,m}?         # Between n and m (lazy)

Groups

(abc)          # Capturing group
(?:abc)        # Non-capturing group
(a|b)          # OR - matches 'a' or 'b'
(?=abc)        # Positive lookahead
(?!abc)        # Negative lookahead
(?<=abc)       # Positive lookbehind
(?<!abc)       # Negative lookbehind
(?#comment)    # Comment (some engines)

Escape Characters

Special characters that need escaping:

\.             # Literal dot (not any character)
\*             # Literal asterisk (not zero or more)
\+             # Literal plus (not one or more)
\?             # Literal question mark (not zero or one)
\^             # Literal caret (not start of line)
\$             # Literal dollar sign (not end of line)
\[             # Literal opening bracket
\]             # Literal closing bracket
\{             # Literal opening brace
\}             # Literal closing brace
\(             # Literal opening parenthesis
\)             # Literal closing parenthesis
\|             # Literal pipe (not OR)
\\             # Literal backslash

Common Patterns

Email Validation

[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}

Phone Number (US)

\+?\d{1,3}[-.\s]?\(?\d{3}\)?[-.\s]?\d{3}[-.\s]?\d{4}

URL

https?://(?:[\w-]+\.)+[\w-]+(?:/[\w-./?%&=]*)?

IPv4 Address

\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}

IPv6 Address

(?:[0-9a-fA-F]{1,4}:){7}[0-9a-fA-F]{1,4}

Date (YYYY-MM-DD)

\d{4}-\d{2}-\d{2}

Date (MM/DD/YYYY)

\d{2}/\d{2}/\d{4}

Time (HH:MM:SS)

([01]?[0-9]|2[0-3]):[0-5][0-9]:[0-5][0-9]

Credit Card (Basic)

\d{4}[- ]?\d{4}[- ]?\d{4}[- ]?\d{4}

Hex Color Code

#[0-9a-fA-F]{3}(?:[0-9a-fA-F]{3})?

Username

^[a-zA-Z0-9_]{3,20}$

Password (Strong)

^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[@$!%*?&])[A-Za-z\d@$!%*?&]{8,}$

HTML Tags

<([a-z]+)([^<]+)*(?:>(.*)<\/\1>|\s+\/>)

XML Tags

<([^>]+)>(.*?)<\/\1>

JSON Key

"[^"]+"\s*:

JSON String Value

:\s*"([^"\\]|\\.)*"

Practical Examples

Extract All Numbers

\d+(?:\.\d+)?

Example:

Text: The price is $19.99 and $25.50
Matches: "19.99", "25.50"

Extract All Emails

[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}

Example:

Text: Contact us at [email protected] or [email protected]
Matches: "[email protected]", "[email protected]"

Extract All URLs

https?://[^\s/$.?#].[^\s]*

Example:

Text: Visit https://example.com/page or http://test.org
Matches: "https://example.com/page", "http://test.org"

Remove Extra Whitespace

\s+

Replacement: Single space

Example:

Text: Hello    world!
Result: Hello world!

Find Repeated Words

\b(\w+)\s+\1\b

Example:

Text: This is is a test test
Matches: "is is", "test test"

Match Quoted Strings

"[^"\\]|\\.)*"

Example:

Text: He said "hello" and "goodbye"
Matches: "hello", "goodbye"

Extract Hashtags

#\w+

Example:

Text: Check out #regex and #programming tips
Matches: "#regex", "#programming"

Extract Mentions

@\w+

Example:

Text: Thanks @user1 and @user2 for helping!
Matches: "@user1", "@user2"

Modifiers (Flags)

Case Insensitive

/i

Matches both uppercase and lowercase letters.

Multiline

/m

Makes ^ and $ match start/end of each line, not just string.

Global

/g

Find all matches, not just the first.

Dot Matches All

/s

Makes . match newline characters too.

Unicode

/u

Enable full Unicode support.

Sticky

/y

Matches only from the index indicated by lastIndex.

Lookarounds

Positive Lookahead

Match something only if it's followed by something else.

\w+(?=abc)

Matches word only if followed by "abc".

Negative Lookahead

Match something only if it's NOT followed by something else.

\w+(?!abc)

Matches word only if NOT followed by "abc".

Positive Lookbehind

Match something only if it's preceded by something else.

(?<=abc)\w+

Matches word only if preceded by "abc".

Negative Lookbehind

Match something only if it's NOT preceded by something else.

(?<!abc)\w+

Matches word only if NOT preceded by "abc".

Advanced Patterns

Validating Password Strength

# At least 8 characters, 1 uppercase, 1 lowercase, 1 digit
^(?=.*[a-z])(?=.*[A-Z])(?=.*\d).{8,}$

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

# At least 12 characters, mixed case, digit, special
^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[@$!%*?&])[A-Za-z\d@$!%*?&]{12,}$

Extracting Domain from Email

@([a-zA-Z0-9.-]+\.[a-zA-Z]{2,})

Matching Balanced Parentheses

\(([^()]|(?R))*\)

(Recursive pattern, supported by some engines)

Validating Credit Card (Luhn Algorithm)

^(?:4[0-9]{12}(?:[0-9]{3})?|5[1-5][0-9]{14}|6(?:011|5[0-9]{2})[0-9]{12}|3[47][0-9]{13}|3(?:0[0-5]|[68][0-9])[0-9]{11}|(?:2131|1800|35\d{3})\d{11})$

Matching HTML Attributes

([a-z-]+)=("[^"]*"|'[^']*')

Extracting CSS Values

([a-z-]+):\s*([^;]+)

Language-Specific Patterns

JavaScript

// Match JavaScript function
function\s+(\w+)\s*\([^)]*\)\s*\{[^}]*\}

// Match JavaScript variable
var\s+(\w+)\s*=\s*([^;]+)

// Match JavaScript object property
\w+\.\w+

Python

# Match Python function
def\s+(\w+)\s*\([^)]*\)\s*:.*?(?=\ndef\s|\Z)

# Match Python import
^import\s+([a-zA-Z0-9_]+)

# Match Python class
class\s+(\w+).*?(?=\nclass\s|\Z)

Java

// Match Java method
(?:public|private|protected)?\s*(?:static)?\s*(?:\w+\s+)+(\w+)\s*\([^)]*\)\s*\{[^}]*\}

// Match Java class
class\s+(\w+).*?{[^}]*}

CSS

/* Match CSS selector */
[a-z-]+\s*\{[^}]*\}

/* Match CSS property */
[a-z-]+\s*:\s*[^;]+;

/* Match CSS class selector */
\.[a-z-]+

SQL

/* Match SQL SELECT */
SELECT\s+[^;]+FROM\s+[^(;]+;

/* Match SQL table name */
FROM\s+([a-zA-Z_][a-zA-Z0-9_]*)

Optimization Tips

Use Character Classes Instead of OR

# Slower
a|b|c|d|e

# Faster
[a-e]

Avoid Catastrophic Backtracking

# Dangerous - can cause exponential backtracking
(a+)+

# Better - more specific
a{1,100}

Use Possessive Quantifiers (When Supported)

# Can backtrack
a.*ab

# No backtracking - faster
a.*+ab

Anchor Your Patterns

# Slower - searches entire string
pattern

# Faster - starts at beginning
^pattern

# Faster - ends at end
pattern$

Be Specific

# Too general
.*

# Better - specific characters
[a-zA-Z0-9]+

Common Tasks

Validate Input

# Email validation
^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$

# Phone number validation
^\+?\d{1,3}[-.\s]?\(?\d{3}\)?[-.\s]?\d{3}[-.\s]?\d{4}$

# Date validation (YYYY-MM-DD)
^\d{4}-\d{2}-\d{2}$

Extract Data

# Extract URLs
https?://[^\s/$.?#].[^\s]*

# Extract emails
[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}

# Extract numbers
\d+(?:\.\d+)?

Clean Text

# Remove HTML tags
<[^>]*>

# Remove extra whitespace
\s+

# Remove special characters
[^a-zA-Z0-9\s]

Find and Replace

# Replace multiple spaces with single
\s+ 
→ single space

# Replace phone number format
(\d{3})[-.](\d{3})[-.](\d{4})
→ ($1) $2-$3

# Replace camelCase with snake_case
([a-z])([A-Z])
→ $1_$2

Quick Tips

Start simple - Begin with literal characters, then add complexity
Test frequently - Use our Regex Tester to verify patterns
Use anchors - Pin your patterns to start/end of strings
Escape special characters - Use \ before . * + ? ^ $ [ ] { } ( ) | \
Consider performance - Avoid nested quantifiers and excessive backtracking
Use character classes - More efficient than multiple OR conditions
Document complex patterns - Add comments when supported
Use lazy quantifiers - When extracting multiple items
Use greedy quantifiers - When capturing maximum content
Practice regularly - Regex takes time and practice to master

Common Errors

Forgot to Escape Special Characters

# Wrong - matches any character
.test

# Correct - matches literal dot
\.test

Overmatching with Greedy Quantifiers

# Wrong - matches too much
<div>.*</div>

# Correct - matches individual tags
<div>.*?</div>

Not Using Anchors

# Wrong - matches anywhere in text
test

# Correct - matches only at start
^test

Catastrophic Backtracking

# Dangerous
(a+)+b
a*a*a*a*a*a*a*a*a*a*a*a*a*a*a*a*a*a*a*a*a*a*a*a*a

# Better
a{1,100}b
a{20}

Testing and Debugging

Use Our Interactive Regex Tester

Paste your test text
Enter your regex pattern
See matches highlighted in real-time
Adjust and iterate quickly

Debugging Checklist

Did you escape special characters?
Are you using the right quantifiers?
Did you use anchors where needed?
Is the pattern case-sensitive?
Are you matching what you expect?
Is performance acceptable?

Common Debugging Steps

Simplify the pattern - Test each component separately
Use character classes - Replace complex patterns with [a-z] etc.
Add anchors - Start with ^ and end with $ to see full match
Test incremental - Build up complexity gradually
Check for typos - Verify special characters and escapes

Resources

Online Tools

Regex Tester - Interactive testing and debugging
Regex Explainer - Understand complex patterns
Regex Generator - Create patterns from examples

Practice

Test patterns with real-world data
Practice common validation scenarios
Build regex for specific use cases
Share and learn from community examples

Further Learning

Lookarounds and advanced techniques
Performance optimization
Language-specific features
Integration with programming languages

Summary

This cheat sheet covers the most common regex patterns, metacharacters, and use cases. Remember:

Character classes match sets of characters
Quantifiers control repetition
Anchors define position
Groups organize and capture
Lookarounds assert context
Escape special characters with backslash

Practice regularly, test thoroughly, and don't be afraid to experiment. With time and experience, you'll become proficient at crafting powerful and efficient regex patterns!

Bookmark this page for quick reference, and use our interactive tools to practice and perfect your regex skills!

Basic Patterns

Literal Characters

Match characters literally:

hello          # Matches "hello"
Regex          # Matches "Regex"
123            # Matches "123"

Character Classes

Match any one character from a set:

[abc]          # Matches 'a', 'b', or 'c'
[a-z]          # Matches any lowercase letter
[A-Z]          # Matches any uppercase letter
[0-9]          # Matches any digit
[a-zA-Z0-9]    # Matches any alphanumeric character
[^abc]         # Matches any character EXCEPT 'a', 'b', or 'c'
[^0-9]         # Matches any non-digit character

Shorthand Character Classes

\d             # Any digit (same as [0-9])
\D             # Any non-digit (same as [^0-9])
\w             # Any word character (same as [a-zA-Z0-9_])
\W             # Any non-word character
\s             # Any whitespace character (space, tab, newline)
\S             # Any non-whitespace character

Metacharacters

Wildcard

.              # Matches any single character (except newline)

Anchors

^              # Start of string or line
$              # End of string or line
\b             # Word boundary
\B             # Non-word boundary

Quantifiers

*              # Zero or more occurrences
+              # One or more occurrences
?              # Zero or one occurrence
{n}            # Exactly n occurrences
{n,}           # n or more occurrences
{n,m}          # Between n and m occurrences
*?             # Zero or more (lazy/non-greedy)
+?             # One or more (lazy)
??             # Zero or one (lazy)
{n,}?          # n or more (lazy)
{n,m}?         # Between n and m (lazy)

Groups

(abc)          # Capturing group
(?:abc)        # Non-capturing group
(a|b)          # OR - matches 'a' or 'b'
(?=abc)        # Positive lookahead
(?!abc)        # Negative lookahead
(?<=abc)       # Positive lookbehind
(?<!abc)       # Negative lookbehind
(?#comment)    # Comment (some engines)

Escape Characters

Special characters that need escaping:

\.             # Literal dot (not any character)
\*             # Literal asterisk (not zero or more)
\+             # Literal plus (not one or more)
\?             # Literal question mark (not zero or one)
\^             # Literal caret (not start of line)
\$             # Literal dollar sign (not end of line)
\[             # Literal opening bracket
\]             # Literal closing bracket
\{             # Literal opening brace
\}             # Literal closing brace
\(             # Literal opening parenthesis
\)             # Literal closing parenthesis
\|             # Literal pipe (not OR)
\\             # Literal backslash

Common Patterns

Email Validation

[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}

Phone Number (US)

\+?\d{1,3}[-.\s]?\(?\d{3}\)?[-.\s]?\d{3}[-.\s]?\d{4}

URL

https?://(?:[\w-]+\.)+[\w-]+(?:/[\w-./?%&=]*)?

IPv4 Address

\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}

IPv6 Address

(?:[0-9a-fA-F]{1,4}:){7}[0-9a-fA-F]{1,4}

Date (YYYY-MM-DD)

\d{4}-\d{2}-\d{2}

Date (MM/DD/YYYY)

\d{2}/\d{2}/\d{4}

Time (HH:MM:SS)

([01]?[0-9]|2[0-3]):[0-5][0-9]:[0-5][0-9]

Credit Card (Basic)

\d{4}[- ]?\d{4}[- ]?\d{4}[- ]?\d{4}

Hex Color Code

#[0-9a-fA-F]{3}(?:[0-9a-fA-F]{3})?

Username

^[a-zA-Z0-9_]{3,20}$

Password (Strong)

^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[@$!%*?&])[A-Za-z\d@$!%*?&]{8,}$

HTML Tags

<([a-z]+)([^<]+)*(?:>(.*)<\/\1>|\s+\/>)

XML Tags

<([^>]+)>(.*?)<\/\1>

JSON Key

"[^"]+"\s*:

JSON String Value

:\s*"([^"\\]|\\.)*"

Practical Examples

Extract All Numbers

\d+(?:\.\d+)?

Example:

Text: The price is $19.99 and $25.50
Matches: "19.99", "25.50"

Extract All Emails

[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}

Example:

Text: Contact us at [email protected] or [email protected]
Matches: "[email protected]", "[email protected]"

Extract All URLs

https?://[^\s/$.?#].[^\s]*

Example:

Text: Visit https://example.com/page or http://test.org
Matches: "https://example.com/page", "http://test.org"

Remove Extra Whitespace

\s+

Replacement: Single space

Example:

Text: Hello    world!
Result: Hello world!

Find Repeated Words

\b(\w+)\s+\1\b

Example:

Text: This is is a test test
Matches: "is is", "test test"

Match Quoted Strings

"[^"\\]|\\.)*"

Example:

Text: He said "hello" and "goodbye"
Matches: "hello", "goodbye"

Extract Hashtags

#\w+

Example:

Text: Check out #regex and #programming tips
Matches: "#regex", "#programming"

Extract Mentions

@\w+

Example:

Text: Thanks @user1 and @user2 for helping!
Matches: "@user1", "@user2"

Modifiers (Flags)

Case Insensitive

/i

Matches both uppercase and lowercase letters.

Multiline

/m

Makes ^ and $ match start/end of each line, not just string.

Global

/g

Find all matches, not just the first.

Dot Matches All

/s

Makes . match newline characters too.

Unicode

/u

Enable full Unicode support.

Sticky

/y

Matches only from the index indicated by lastIndex.

Lookarounds

Positive Lookahead

Match something only if it's followed by something else.

\w+(?=abc)

Matches word only if followed by "abc".

Negative Lookahead

Match something only if it's NOT followed by something else.

\w+(?!abc)

Matches word only if NOT followed by "abc".

Positive Lookbehind

Match something only if it's preceded by something else.

(?<=abc)\w+

Matches word only if preceded by "abc".

Negative Lookbehind

Match something only if it's NOT preceded by something else.

(?<!abc)\w+

Matches word only if NOT preceded by "abc".

Advanced Patterns

Validating Password Strength

# At least 8 characters, 1 uppercase, 1 lowercase, 1 digit
^(?=.*[a-z])(?=.*[A-Z])(?=.*\d).{8,}$

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

# At least 12 characters, mixed case, digit, special
^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[@$!%*?&])[A-Za-z\d@$!%*?&]{12,}$

Extracting Domain from Email

@([a-zA-Z0-9.-]+\.[a-zA-Z]{2,})

Matching Balanced Parentheses

\(([^()]|(?R))*\)

(Recursive pattern, supported by some engines)

Validating Credit Card (Luhn Algorithm)

^(?:4[0-9]{12}(?:[0-9]{3})?|5[1-5][0-9]{14}|6(?:011|5[0-9]{2})[0-9]{12}|3[47][0-9]{13}|3(?:0[0-5]|[68][0-9])[0-9]{11}|(?:2131|1800|35\d{3})\d{11})$

Matching HTML Attributes

([a-z-]+)=("[^"]*"|'[^']*')

Extracting CSS Values

([a-z-]+):\s*([^;]+)

Language-Specific Patterns

JavaScript

// Match JavaScript function
function\s+(\w+)\s*\([^)]*\)\s*\{[^}]*\}

// Match JavaScript variable
var\s+(\w+)\s*=\s*([^;]+)

// Match JavaScript object property
\w+\.\w+

Python

# Match Python function
def\s+(\w+)\s*\([^)]*\)\s*:.*?(?=\ndef\s|\Z)

# Match Python import
^import\s+([a-zA-Z0-9_]+)

# Match Python class
class\s+(\w+).*?(?=\nclass\s|\Z)

Java

// Match Java method
(?:public|private|protected)?\s*(?:static)?\s*(?:\w+\s+)+(\w+)\s*\([^)]*\)\s*\{[^}]*\}

// Match Java class
class\s+(\w+).*?{[^}]*}

CSS

/* Match CSS selector */
[a-z-]+\s*\{[^}]*\}

/* Match CSS property */
[a-z-]+\s*:\s*[^;]+;

/* Match CSS class selector */
\.[a-z-]+

SQL

/* Match SQL SELECT */
SELECT\s+[^;]+FROM\s+[^(;]+;

/* Match SQL table name */
FROM\s+([a-zA-Z_][a-zA-Z0-9_]*)

Optimization Tips

Use Character Classes Instead of OR

# Slower
a|b|c|d|e

# Faster
[a-e]

Avoid Catastrophic Backtracking

# Dangerous - can cause exponential backtracking
(a+)+

# Better - more specific
a{1,100}

Use Possessive Quantifiers (When Supported)

# Can backtrack
a.*ab

# No backtracking - faster
a.*+ab

Anchor Your Patterns

# Slower - searches entire string
pattern

# Faster - starts at beginning
^pattern

# Faster - ends at end
pattern$

Be Specific

# Too general
.*

# Better - specific characters
[a-zA-Z0-9]+

Common Tasks

Validate Input

# Email validation
^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$

# Phone number validation
^\+?\d{1,3}[-.\s]?\(?\d{3}\)?[-.\s]?\d{3}[-.\s]?\d{4}$

# Date validation (YYYY-MM-DD)
^\d{4}-\d{2}-\d{2}$

Extract Data

# Extract URLs
https?://[^\s/$.?#].[^\s]*

# Extract emails
[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}

# Extract numbers
\d+(?:\.\d+)?

Clean Text

# Remove HTML tags
<[^>]*>

# Remove extra whitespace
\s+

# Remove special characters
[^a-zA-Z0-9\s]

Find and Replace

# Replace multiple spaces with single
\s+ 
→ single space

# Replace phone number format
(\d{3})[-.](\d{3})[-.](\d{4})
→ ($1) $2-$3

# Replace camelCase with snake_case
([a-z])([A-Z])
→ $1_$2

Quick Tips

Start simple - Begin with literal characters, then add complexity
Test frequently - Use our Regex Tester to verify patterns
Use anchors - Pin your patterns to start/end of strings
Escape special characters - Use \ before . * + ? ^ $ [ ] { } ( ) | \
Consider performance - Avoid nested quantifiers and excessive backtracking
Use character classes - More efficient than multiple OR conditions
Document complex patterns - Add comments when supported
Use lazy quantifiers - When extracting multiple items
Use greedy quantifiers - When capturing maximum content
Practice regularly - Regex takes time and practice to master

Common Errors

Forgot to Escape Special Characters

# Wrong - matches any character
.test

# Correct - matches literal dot
\.test

Overmatching with Greedy Quantifiers

# Wrong - matches too much
<div>.*</div>

# Correct - matches individual tags
<div>.*?</div>

Not Using Anchors

# Wrong - matches anywhere in text
test

# Correct - matches only at start
^test

Catastrophic Backtracking

# Dangerous
(a+)+b
a*a*a*a*a*a*a*a*a*a*a*a*a*a*a*a*a*a*a*a*a*a*a*a*a

# Better
a{1,100}b
a{20}

Testing and Debugging

Use Our Interactive Regex Tester

Paste your test text
Enter your regex pattern
See matches highlighted in real-time
Adjust and iterate quickly

Debugging Checklist

Did you escape special characters?
Are you using the right quantifiers?
Did you use anchors where needed?
Is the pattern case-sensitive?
Are you matching what you expect?
Is performance acceptable?

Common Debugging Steps

Simplify the pattern - Test each component separately
Use character classes - Replace complex patterns with [a-z] etc.
Add anchors - Start with ^ and end with $ to see full match
Test incremental - Build up complexity gradually
Check for typos - Verify special characters and escapes

Resources

Online Tools

Regex Tester - Interactive testing and debugging
Regex Explainer - Understand complex patterns
Regex Generator - Create patterns from examples

Practice

Test patterns with real-world data
Practice common validation scenarios
Build regex for specific use cases
Share and learn from community examples

Further Learning

Lookarounds and advanced techniques
Performance optimization
Language-specific features
Integration with programming languages

Summary

This cheat sheet covers the most common regex patterns, metacharacters, and use cases. Remember:

Character classes match sets of characters
Quantifiers control repetition
Anchors define position
Groups organize and capture
Lookarounds assert context
Escape special characters with backslash

Practice regularly, test thoroughly, and don't be afraid to experiment. With time and experience, you'll become proficient at crafting powerful and efficient regex patterns!

Bookmark this page for quick reference, and use our interactive tools to practice and perfect your regex skills!