Regular Expression Tester and Visualizer

You can make use of $1, $2, $3 and so on if you are using parenthesis groups in your regular expression. \t \n \r are supported.

Error Message

What is a regular expression?

A regular expression (also known as regex or regexp) is a search pattern consisting of a set of characters and optional flags. You can use a regular expression to define a search pattern to find data in a text.


Flags or modifiers in regular expressions are used to customize searching.

Flag Description
g Global match - finds all matches instead of stopping at the first one
i Ignore case - performs a case insensitive search
m Multiline - allows ^ and $ to match start and end of line
u Unicode - enables full Unicode support
y Sticky - starts searching at the lastIndex position
s Singleline - also known as "dotall", allows . to match newlines \n


Brackets are used to search for characters in a given range in regular expressions.

Expression Description
[...] One of the characters in the brackets
[^...] One of the characters NOT in the brackets
[a-z] One of the characters from a to z
[^a-z] One of the characters NOT from a to z
[A-Z] One of the characters from A to Z
[^A-Z] One of the characters NOT from A to Z
[0-9] One of the characters from 0 to 9 (a digit character)
[^0-9] One of the characters NOT from 0 to 9 (a non-digit character)


Groups in regular expressions are part of a search pattern enclosed in parentheses (...).

Expression Description
(...) A capturing group
(?:...) A non-capturing group
(a|b) Either a or b

Character Classes

Character classes are characters with a special meaning to define search patterns in regular expressions.

Character Description
. A single character except newline \n
\d A digit character. Equivalent to [0-9].
\D A non-digit character. Equivalent to [^0-9].
\w A word character. An alphanumeric character including underscore. Equivalent to [a-zA-Z0-9_].
\W A non-word character. NOT an alphanumeric character including underscore. Equivalent to [^a-zA-Z0-9_].
\s A whitespace character
\S A non-whitespace character
[\b] A literal backspace character

Special Characters

Character Description
\ An escape character
\0 A null character
\n A newline character
\t A tab character
\v A vertical tab character
\r A carriage return character
\f A form feed character
\cX A control character where X is a character from A-Z
\ooo The character specified by three octal digits
\xhh The character specified by two hexadecimal digits
\uhhhh The Unicode character specified by four hexadecimal digits


Quantifiers in regular expressions specify the number of occurrences a character, character class, or group must be present.

Character Description
* Zero or more times
? Zero or one time
+ One or more times
{n} Exactly n times
{n,m} n to m times
{n,} n times or more


Assertions are regular expressions consisting of anchors and lookaheads that cause a match to succeed if found or fail otherwise.

Character Description
^ Start of string or line
$ End of string or line
\b A word boundary
\B A non-word boundary
(?=...) Positive lookahead
(?!...) Negative lookahead