Carrot2 is a free, open source search clustering engine with additional document categorization functions. For each set of search terms, Carrot2 provides a topic tree and subtopics built from the search results, and generates visualizations that enable users to quickly overview their search. Searches can be filtered according to source, such as Bing, image files or the Wikipedia, results can be clustered according to several presets such as K-means or URL, or filtered by country and langauge. Carrot2 enables users to download results in ranges from 50 to 200 for further analysis.