Evercookie is designed to make persistent data just that, persistent. By storing the same data in several locations that a client can access, if any of the data is ever lost (for example, by clearing cookies), the data can be recovered and then reset and reused. Simply think of it as cookies that just won’t go away. Evercookie is a javascript API available that produces extremely persistent cookies in a browser. Its goal is to identify a client even after they’ve removed standard cookies, Flash cookies (Local Shared Objects or LSOs), and others. Evercookie accomplishes this by storing the cookie data in several types of storage mechanisms that are available on the local browser. Additionally, if Evercookie has found the user has removed any of the types of cookies in question, it recreates them using each mechanism available.
An Evercookie is not merely difficult to delete. It actively “resists” deletion by copying itself in different forms on the user’s machine and resurrecting itself if it notices that some of the copies are missing or expired.[10] Specifically, when creating a new cookie, Evercookie uses the following storage mechanisms when available:
