How are clusters created ?
Keywords are grouped together based on the percentage of URLs that they share in the top 10 search results with the main keyword, which is the keyword with the highest search volume in the cluster.
In order to be grouped together, keywords must have at least a 40% overlap in their URLs.
When you click on the cluster title, you will see a list of the keywords included in that cluster, along with a percentage sign indicating the similarity of their top 10 search engine results pages (SERPs) with the main keyword.
Clustering is done using live search results data, so you can be confident that you are getting the most up-to-date insights.
PS: It is possible to adjust the percentage of URL overlap required for keywords to be included in the same cluster (see settings), as well as the number of search results to take into account.