Regex Cheat Sheet

hello     # Matches "hello"

.         # Any single character
h.t       # hat, hit, hot, h@t

\.        # Literal dot
\$        # Literal dollar sign
\(\)      # Literal parentheses

^start    # Start of line
end$      # End of line
^exact$   # Exact match
\bword\b  # Word boundary

[abc]     # a, b, or c
[^abc]    # NOT a, b, or c
[a-z]     # Any lowercase letter
[A-Za-z]  # Any letter
[0-9]     # Any digit

\d        # Digit [0-9]
\D        # Non-digit
\w        # Word char [A-Za-z0-9_]
\W        # Non-word char
\s        # Whitespace
\S        # Non-whitespace

[:alpha:] # Letters
[:digit:] # Digits
[:alnum:] # Alphanumeric
[:space:] # Whitespace

a*        # 0 or more
a+        # 1 or more
a?        # 0 or 1
a{3}      # Exactly 3
a{2,4}    # 2 to 4
a{2,}     # 2 or more

.*        # Greedy (match most)
.*?       # Lazy (match least)
.+?       # Lazy 1 or more
.{2,4}?   # Lazy range

\d+       # One or more digits
\w{3,8}   # 3-8 word characters
https?    # http or https

(abc)     # Capture "abc"
(\d{3})-(\d{4})  # Phone parts

(?:abc)   # Group without capture

cat|dog   # cat OR dog
(jpg|png|gif)  # Image extensions

(\w+) \1  # Repeated word
(['"]).*?\1  # Matching quotes

(?<name>\w+)  # Named capture
\k<name>      # Named backreference

foo(?=bar)    # foo followed by bar
\d+(?=px)     # Digits before "px"

foo(?!bar)    # foo NOT followed by bar
\d+(?!px)     # Digits not before "px"

(?<=\$)\d+   # Digits after "$"
(?<=@)\w+    # Word after "@"

(?<!\$)\d+   # Digits not after "$"

[\w.-]+@[\w.-]+\.\w+

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

\(?\d{3}\)?[-. ]?\d{3}[-. ]?\d{4}

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

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

#[0-9A-Fa-f]{6}\b

^[a-zA-Z][a-zA-Z0-9_]{2,15}$

/pattern/i    # JavaScript
(?i)pattern   # Inline flag

/pattern/g    # Match all

/pattern/m    # ^ and $ match line breaks

/pattern/s    # . matches newlines

/pattern/gim  # Multiple flags