Abstract: A probabilistic hash map can be used to store category information for large numbers of website in a relatively small amount of data. Retrieving the values can be performed with high accuracy and speed. The map consists of a set of buckets capable of storing data. Values are programmed into or retrieved from the map for each key by storing or retrieving the value(s) in association with an initial hash of the key within a subset of buckets of the map, the subset of buckets being selected based on additional hashes of the key. Value(s) can be stored inherently or via reference to a value index, which itself can embed values or further reference to larger payloads of value information.