Regular expressions in Looker Studio

A regular expression (regexp) is a specific sequence of characters that broadly or narrowly matches patterns in your data. You can use regular expressions to create more flexible filters in charts and controls. You can also use the following regular expression functions in calculated field formulas:

REGEXP_CONTAINS	Returns true if the input value contains the regular expression pattern, otherwise returns false. Learn more about REGEXP_CONTAINS.
REGEXP_EXTRACT	Returns the first matching substring in the input value that matches the regular expression pattern. Learn more about REGEXP_EXTRACT.
REGEXP_MATCH	Returns true if the input value matches the regular expression pattern, otherwise returns false. Learn more about REGEXP_MATCH.
EGEXP_REPLACE	Replaces all occurrences of text that match the regular expression pattern in the input value with the replacement string. Learn more about EGEXP_REPLACE.

Alternatives to using regular expressions

Constructing regular expressions can be complex. Before using a regexp function, consider whether using a simpler text function will achieve your goal. The following functions provide regular expression-like functionality without requiring you to know regexp syntax.

Function	Description
CONTAINS_TEXT	Returns true if the specified text is found in the field or expression, otherwise returns false.
ENDS_WITH	Returns true if the field or expression ends with the specified text, otherwise returns false.
LEFT_TEXT	Returns a number of characters from the beginning of a specified string.
REPLACE	Returns a copy of the original text with all occurrences of the search text substituted with the replacement text.
RIGHT_TEXT	Returns a number of characters from the end of a specified string.
STARTS_WITH	Returns true if the field or expression begins with the specified text, otherwise returns false.
TRIM	Returns text with leading and trailing spaces removed.

Regular expression examples

Matches if MyField contains space characters:

REGEXP_CONTAINS(MyField, "\\s+")

Extracts the top-level directory in a URL:

REGEXP_EXTRACT(URL, ^https://[^/]+/([^/]+)/)

For example, if the URL field contained this page's address, the previous function would return looker-studio.

Categorize ad campaigns by language:

CASE
    WHEN REGEXP_MATCH(Campaign 2, R".*\|\s*en\s*\|.*") then "English"
    WHEN REGEXP_MATCH(Campaign 2, R".*\|\s*es\s*\|.*") then "Spanish"
    ELSE "Other language"
END

For example, applying this regular expression to the Campaign dimension in the Google Analytics Demo account gives these results:

Campaign	Language
Campaign #1	Other language
1000549 | Google Analytics Demo | DR | apontes | NA | US | en | Hybrid | AW SEM | BKWS | ~ AW - Google Brand (US)	English
1000549 | Google Analytics Demo | DR | apontes | NA | CA | es | Hybrid | AW SEM | BKWS | ~ AW - YouTube (CA)	Spanish

Swap the order of sections in a string:

REGEXP_REPLACE(Campaign, R'(.*):(.*)', R'\2 \1')

In the previous example, the sections are separated by a colon (:).

Metacharacters

Metacharacters are characters that have special meaning in a regular expression. Following are some of the more common metacharacters you can use. Note that these examples will open in the Google Analytics Help Center, but the information presented there applies equally to Looker Studio.

Note: See google/RE2 GitHub documentation for complete regular expression syntax.

Wildcards

.	Matches any single character (letter, number, or symbol).	1. matches 10, 1A 1.1 matches 111, 1A1 Examples
?	Matches the preceding character 0 or 1 times.	10? matches 1, 10 Examples
+	Matches the preceding character 1 or more times.	10+ matches 10, 100 Examples
*	Matches the preceding character 0 or more times.	1* matches 1, 10 Examples
|	Creates an OR match. Don't use at the end of an expression.	1|10 matches 1, 10 Examples

Anchors

^	Matches the adjacent characters at the beginning of a string.	^10 matches 10 , 10 0, 10 x ^10 does not match 1 10 , 1 10 x Examples
$	Matches the adjacent characters at the end of a string.	10$ matches 1 10 , 10 10 10$ does not match 10 0, 10 x Examples

Groups

( )	Matches the enclosed characters in exact order anywhere in a string. Also used to group other expressions.	(10) matches 10 , 10 1, 10 11 ([0-9]|[a-z]) matches any number or lowercase letter Examples
[ ]	Matches the enclosed characters in any order anywhere in a string.	[10] matches 01 2, 1 20, 2 10 Examples
-	Creates a range of characters within brackets to match anywhere in a string.	[0-9] matches any number 0 through 9 Examples

Escape

\\

Indicates that the adjacent character should be interpreted literally rather than as a regex metacharacter.

\\ indicates that the adjacent dot should be interpreted as a period or decimal rather than as a wildcard 216\\.239\\.32\\.34 matches 216.239.32.34 Examples

Character classes

\d	digits (≡ [0-9])
\D	not digits (≡ [^0-9])
\s	whitespace (≡ [\t\n\f\r ])
\S	not whitespace (≡ [^\t\n\f\r ])
\w	word characters (≡ [0-9A-Za-z_])
\W	not word characters (≡ [^0-9A-Za-z_])

Tips

Use simple expressions

Keep your regular expressions simple. Simple expressions are easier for another user to interpret and modify.

Case-sensitivity

Regular expressions are case-sensitive by default. You can make the match case-insensitive by using the (?i) flag. For example, this expression extracts both "abc123" and "ABC123":

REGEXP_EXTRACT(MyField, '(?i)(a.*)')

Escape the backslash

As previously noted, you use the backslash (\) to escape regular expression metacharacters when you need those characters to be interpreted literally. To match a backslash in a quoted string, you'll need to escape that as well, resulting in two backslashes in your expression. For example:

REGEXP_REPLACE(String, "(\\[.*\\])\\+(\\[.*\\])","\\2 \\1")

As an alternative, consider using the Raw string literal prefix, R:

REGEXP_REPLACE(String, R"(\[.*\])\+(\[.*\])",R"\2 \1")