Evercookie

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Evercookie

Original author(s)	Samy Kamkar
Repository	{{URL|example.com|optional display text}}
Written in	JavaScript
Engine
Operating system	Cross-platform
Type	Web storage

Evercookie is a JavaScript-based application created by Samy Kamkar that produces extremely persistent browser cookies in a web browser. The purpose of Evercookie is to store cookie data in multiple locations on the user's device, making it difficult to delete and ensuring that the data persists even if the user attempts to remove it.

Functionality

Evercookie employs various storage mechanisms to achieve persistence, including:

• HTTP cookies
• Local Shared Objects (commonly known as Flash cookies)
• HTML5 Web Storage (both localStorage and sessionStorage)
• HTML5 IndexedDB
• HTML5 Web SQL Database
• Etags
• Web cache
• window.name
• History API
• HSTS (HTTP Strict Transport Security)

By using these multiple storage methods, Evercookie can recreate the cookie data from any one of these locations if it is deleted from others.

Security and Privacy Concerns

Evercookie raises significant privacy and security concerns because it makes it extremely difficult for users to remove tracking data. This persistence can be exploited by advertisers and malware to track users across different websites and sessions without their consent.

Mitigation

To mitigate the effects of Evercookie, users can:

• Use private browsing or incognito mode which limits the storage of cookies and other data.
• Regularly clear all forms of storage in their browser.
• Use browser extensions designed to block or manage cookies and other tracking mechanisms.
• Disable or limit the use of JavaScript in their browser settings.

See also

• Zombie cookie
• Supercookie
• Browser fingerprinting
• Web tracking
• Privacy software

Related pages

• HTTP cookie
• Local Shared Object
• Web storage
• IndexedDB
• Web SQL Database
• Etag
• Web cache
• window.name
• History API
• HSTS
• Private browsing
• Browser extension
• JavaScript