US Patent 11233866 Methods and apparatus to monitor online activity

Methods and apparatus are disclosed to monitory online activity. An example apparatus includes at least one processor, and memory including instructions that, when executed, cause the at least one processor to compare first uniform resource locators collected from a first client device of a known panelist with second uniform resource locators collected from second client devices associated with one or more users, the one or more users being unknown, and associate at least some of the second uniform resource locators as online activity of the known panelist based on ones of the first uniform resource locators matching at least portions of ones of the second uniform resource locators.