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Evercookie

Evercookie is a Javascript API 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.

This is accomplished by storing the cookie data on as many browser storage mechanisms as possible. If cookie data is removed from any of the storage mechanisms, evercookie aggressively re-creates it in each mechanism as long as one is still intact.

If the Flash LSO, Silverlight or Java mechanism is available, Evercookie can even propagate cookies between different browsers on the same client machine!

By Samy Kamkar, with awesome contributions from others

Browser Storage Mechanisms

Client browsers must support as many of the following storage mechanisms as possible in order for Evercookie to be effective.

To be implemented someday (perhaps by you?):

The Java persistence mechanisms are developed and maintained by Gabriel Bauman over here.

Backend Server

Some of the storage mechanisms require a backend server. This package comes with PHP implementation of the etag, cache and png backend servers.

Caveats

Be warned! Evercookie can potentially cause problems for you or your users.

You are responsible for your own decision to use Evercookie. Choose wisely.

Got an idea?

Open a pull request!