An apparatus, method and system for use in categorising Uniform Resource Locators (URLs) when controlling or monitoring access to the Internet 20 from a client 12. A request message 500 is generated to request categorisation of a specified URL. The request message 500 comprises a licensing field carrying a licence key. A remote server 40 receives the licence key and, if valid, generates a reply message 600 denoting a category of the specified URL. The licence key enables workload at the server 40 to be managed efficiently.