A device implementing a system for anonymizing user data provided for server-side operations includes a processor configured to receive user input including a search term, wherein first and second data structures are stored on the device, the first data structure including user interest data items that correspond to prior user activity, the second data structure including topic data items mapped to the user interest data items, the topic data items being broader than the user interest data items. The processor accesses the second data structure to obtain one or more topic data items. The processor transmits, to a server, the search term and one or more topic data items for obtaining a query suggestion or search result. The processor receives, from the server, the query suggestion or search result, the query suggestion or search result having been obtained based on the search term and one or more topic data items.