A zombie cookie is data and code that has been placed by a web server on a visitor’s computer or other device in a hidden location outside the visitor’s web browser’s dedicated Cookie storage location, and that automatically recreates a HTTP cookie as a regular Cookie after the original Cookie had been deleted. The zombie cookie may be stored in multiple locations, such as HTML5 Web storage, and other client-side and even server-side locations, and when absence is detected in one of the locations, the missing instance is recreated by the JavaScript code using the data stored in other locations.