Combining sources in Google Analytics using a filter

Understanding where our users come from and how they use our site is essential to improving it. Google Analytics is a great tool for this purpose. One drawback is that traffic from sources which use different subdomains for load balancing - such as Hotmail - shows up as hundreds of different sources.

It's simple to use a filter to combine certain traffic sources into one. With a bit of help from the Analytics Help group, all it takes is to create a custom filter, set the type to "Search and replace", the filter field as "Campaign Source" (NOT "Referral", which was my first attempt), a regular expression for the search string (for example "[a-zA-Z0-9]*\.[a-zA-Z0-9]*\.mail\.live\.com"), and a consolidated string for the replace string (for example "mail.live.com"). The filter might look something like this:



That's it! The filter will be applied to any new traffic, but unfortunately it won't be retroactively applied to old data.