Regex Cheat Sheet & Demo

Learn and test regular expressions with an interactive demo

Regex Tester Demo

Regular Expression

Regex Options

Global (g)

Ignore Case (i)

Multiline (m)

Sticky (y)

Test String

Match Results

Regex Cheat Sheet

Character	Description	Example
`.`	Matches any single character except newline	`a.c` matches "abc"
`\w`	Matches any word character (a-z, A-Z, 0-9, _)	`\w+` matches "hello"
`\W`	Matches any non-word character	`\W` matches "@"
`\d`	Matches any digit (0-9)	`\d+` matches "123"
`\D`	Matches any non-digit	`\D` matches "a"
`\s`	Matches any whitespace (space, tab, newline)	`\s+` matches " "
`\S`	Matches any non-whitespace	`\S` matches "a"
`\b`	Matches a word boundary	`\bcat\b` matches "cat" but not "catch"
`\B`	Matches a non-word boundary	`\Bcat` matches "catch" but not "cat "
`^`	Matches start of string (or line with multiline flag)	`^abc` matches "abc" at start
`$`	Matches end of string (or line with multiline flag)	`abc$` matches "abc" at end
`\`	Escapes special characters	`\.` matches literal "."

Class	Description	Example
`[abc]`	Matches any single character in the set	`[aeiou]` matches "a" in "cat"
`[^abc]`	Matches any single character not in the set	`[^0-9]` matches "a" in "a1"
`[a-z]`	Matches any character in the range	`[a-z]` matches "b" in "abc"
`[A-Z]`	Matches any uppercase letter	`[A-Z]` matches "B" in "ABC"
`[0-9]`	Matches any digit	`[0-9]` matches "5" in "a5b"
`[a-zA-Z0-9]`	Matches any alphanumeric character	`[a-zA-Z0-9]` matches "x" in "x1"

Quantifier	Description	Example
`*`	Matches 0 or more occurrences	`a*` matches "" or "aaa"
`+`	Matches 1 or more occurrences	`a+` matches "a" or "aaa"
`?`	Matches 0 or 1 occurrence	`colou?r` matches "color" or "colour"
`{n}`	Matches exactly n occurrences	`\d{3}` matches "123"
`{n,}`	Matches n or more occurrences	`\d{2,}` matches "1234"
`{n,m}`	Matches between n and m occurrences	`\d{2,4}` matches "123"
`*?`, `+?`, `??`	Non-greedy (lazy) matching	`<.*?>` matches "<p>" in "<p><span>"

Group	Description	Example
`(...)`	Captures a group	`(\d+)` captures "123" in "abc123"
`(?:...)`	Non-capturing group	`(?:\d+)` groups "123" without capturing
`(?<name>...)`	Named capture group	`(?<year>\d{4})` captures "2023" as "year"
`\1`, `\2`	Backreference to captured group	`(\w+)\s\1` matches "word word"
`\|`	Alternation (OR)	`cat\|dog` matches "cat" or "dog"

Assertion	Description	Example
`(?=...)`	Positive lookahead	`\w+(?=\.)` matches "file" in "file.txt"
`(?!...)`	Negative lookahead	`\w+(?!\.)` matches "file" in "filename"
`(?<=...)`	Positive lookbehind	`(?<=\$)\d+` matches "100" in "$100"
`(?<!...)`	Negative lookbehind	`(?<!\$)\d+` matches "100" in "100px"

Flag	Description	Example
`g`	Global: Matches all occurrences	`/a/g` matches all "a"s in "aba"
`i`	Ignore case: Case-insensitive matching	`/a/i` matches "A" or "a"
`m`	Multiline: ^ and $ match line start/end	`/^a/m` matches "a" at start of each line
`y`	Sticky: Matches only at lastIndex	`/a/y` matches "a" at specific position
`u`	Unicode: Enables full Unicode matching	`/\p{L}/u` matches any Unicode letter
`s`	Dotall: . matches newlines	`/a.b/s` matches "a\nb"

Pattern	Description	Example
`[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}`	Matches an email address	Matches "user@example.com"
`https?:\/\/[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}(\/[^\s]*)?`	Matches a URL	Matches "https://example.com/path"
`\+?\d{1,3}[-.\s]?\d{3}[-.\s]?\d{4}`	Matches a phone number	Matches "+1-555-123-4567"
`#?[0-9a-fA-F]{6}`	Matches a hex color code	Matches "#FF0000"
`\d{4}-\d{2}-\d{2}`	Matches a date (YYYY-MM-DD)	Matches "2023-12-31"
`\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}`	Matches an IPv4 address	Matches "192.168.1.1"

Tips for Using Regex

Use the demo above to test patterns from the cheat sheet
Escape special characters with \ (e.g., \. for literal dot)
Enable flags like Global (g) or Ignore Case (i) in the demo for different behaviors
Test with varied inputs to ensure patterns are robust
Use named capture groups (?...) for clarity