Regular expression is a powerful way to target complicated URLs or to simplify complex conditions into a single query.


How does a regular expression (regex) work?

In regular expression you combine literal characters with special characters to create a logical pattern. This logical pattern then defines which URLs will be targeted and which will be out of scope.


  • Literal character = any character of your URL, such as "w" or "/" from "www.examplepage.com/page"
  • Special character = a character having special meaning, such as "\d" means represents any single digit


Please note, that some characters common in the URL (such as / or .) is by considered special by regex. Therefore if they are meant literally, it is necessary to always put "\" in front of them. The common URL will then look like "www\.examplepage\.com\/page".


Examples of regular expressions

Regular expressionURLs that will be targetedMore information
^www\.examplepage\.com$An exact match of www.examplepage.com.

URLs containing specific pages (such as www.examplepage.com/page) will be excluded!
^ signals that the URL must start there
$ signals that the URL must end there
examplepage\.com\/id\/\d+\/editexamplepage.com/id/<number>/edit

All URLs containing "examplepage.com/id/", then number of any length and then "/edit" will be targeted
\d represents any digit
+ signals the previous sign is present one or more times

Together (\d+) they mean one or more digits.
examplepage\.(com|net)Any URL containing examplepage.com or examplepage.net| signals that word before or word after needs to be there

The condition can be put inside of ( ) for better readability.


Special characters (essentials)

^
start of string
$end of string
a+one or more of a
a*zero or more of a
a?zero or one of a
a{3}exactly 3x a
a{3,}3x or more of a
a{3,5}Between 3x and 5x of a
a|ba or b
\dany digit
\D
any non-digit
.any single character
[abc]a single character from a, b or c
[^abc]a single character except a, b or c
[a-z]a single character in range from a to z



Testing your regular expressions

You can use the tool https://regex101.com/ to test your regular expressions.