The PNS URL filter checks the URLs of HTTP requests against a categorized database. The URLs and domains in the database are organized into thematic categories such as adult, health, business, and so on. If the requested URL is listed in the database, the categories matching the URL are assigned to the request. PNS can accept, redirect, or reject the HTTP request based on its assigned categories.

Typically, accessing a webpage involves several HTTP requests. URL filtering is applied to every HTTP request, so different parts of the webpage can belong to different categories. PNS can remove content belonging to unwanted categories while permitting access to the remaining content. For example, this can be used to prohibit access to advertisements or videos while permitting access to other parts of the website.