A system comprising: at least one hardware processor; and a non-transitory computer-readable storage medium having program instructions embodied therewith, the program instructions executable by said at least one hardware processor to, automatically: receive, from each of a plurality of web clients, a request to receive data, wherein said data comprises (i) advertisement copy and (ii) a landing page URL (Uniform Resource Locator) associated with said advertisement copy; determine, for each of said web clients, a client identifier associated with said web client; automatically select a subset of said web clients; send said data only to said subset of said web clients; and identify a web client not included in said subset of web clients is a software robot, when a received redirection request to said landing page URL is associated with a client identifier associated with said web client.