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 and reading out Web History
• Storing cookies in HTTP ETags
• Internet Explorer userData storage
• HTML5 Session Storage
• HTML5 Local Storage
• HTML5 Global Storage
• HTML5 Database Storage via SQLite

Previously, previously.