Abstract: When an in-app event, which may be any activity that occurs within a mobile application, is performed, a server may receive in-app data including a device identifier associated with a device from which the in-app event originated. The server may generate all permutations of the received device identifier, including all hashed versions of the device identifier, and store all device identifiers associated with the device in a data record. Any other click events with click data including a device identifier that matches any of the device identifiers in the data record can be recognized as originating from the same device. Hence, mobile activity may be tracked to the actual device at which the activity occurred, despite existing device identifier fragmentation. This can enable more effective analysis, such as click fraud analysis and click path analysis, of click traffic for display campaigns.