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Zombie cookies

(also persistent cookies, evercookies)

Zombie cookies definition

Zombie cookies, also known as persistent cookies or evercookies, represent a type of HTTP cookie that recreates itself after deletion from a user's browser. Unlike standard cookies, zombie cookies utilize a web browser’s various data storage mechanisms simultaneously so that they can reactivate when a user tries to delete them.

See also: first-party cookie, flash cookies, persistent cookie, secure cookie, session cookie, third-party cookie, tracking cookie

Zombie cookies examples

  • Online advertising: Advertisers use zombie cookies to persistently track user behavior online to understand their preferences and serve them targeted ads.
  • Website personalization: Some websites may use zombie cookies to remember a user's preferences, enhancing their experience during subsequent visits.

Advantages and disadvantages of zombie cookies for advertisers


  • Persistent data: Zombie cookies enable the retention of user data across sessions, leading to improved personalization and usability.
  • Advertising: They allow businesses to collect comprehensive data on user behavior and preferences, facilitating more effective targeted advertising.


  • Invasiveness: Zombie cookies are widely criticized for their invasiveness, given their persistence and the difficulty in removing them.
  • Privacy concerns: They pose significant privacy issues, as they can be used to track users' online activities without their consent and are considered unethical

Managing zombie cookies

  • Use browser settings and privacy tools that can detect and remove zombie cookies.