Wednesday, September 22, 2010

Evercookie - Virtually Irrevocable Persistent Cookies

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.

Specifically, when creating a new cookie, it uses the following storage mechanisms when available:
  • Standard HTTP Cookies
  • Local Shared Objects (Flash Cookies)
  • Storing cookies in RGB values of auto-generated, force-cached PNGs using HTML5 Canvas tag to read pixels (cookies) back out
  • Storing cookies in Web History (seriously. see FAQ)
  • HTML5 Session Storage
  • HTML5 Local Storage
  • HTML5 Global Storage
  • HTML5 Database Storage via SQLite


evercookie is written in JavaScript and additionally uses a SWF (Flash) object for the Local Shared Objects and PHP for the server-side generation of cached PNGs.

v0.1 BETA, released 09/20/2010 - download source here

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