URL categorization in a Chrome Extension

I have a Chrome extension that records the date, time spent, and url of sites visited in a popup window. I would like to categorize the urls into five (or more) basic categories and place that category in the popup. I have seen web categorization APIs online. However, perhaps this is more simple than that. I just want to scan the url and then pretty much attach a label to it and display it. For example, anything with the word store in it could be categorized as "Retail" or .gov as "Government". What is the best way to do this?