How are Traffic sources categorized?

When looking at the Traffic sources section, I understand that Clicky looks at the referrer and then assigns it to a category (e.g. facebook.com would land in Social media; gmail.com would land in Email). Is there any documentation on how these categorizations take place or how frequently the definitions change (e.g. a new domain is added to Social media)?

My bottom line question is: Is it valid to compare Links year-over-year or Social media year-over-year? Or do the categorizations change too frequently to make such comparisons?

Hi, it's all based on referring domain, except for "advertising" will also apply if there's a campaign involved, either one you define in Clicky or one that uses "UTM" parameters.

We don't have a public list of which domains apply to which sources. And some of it is based on keyword string matching, particularly for the "advertising" category, since there are about 10 billion different domains related to advertising.

This article has a brief summary of each category:

https://clicky.com/help/faq/features/traffic-sources