A Flash cookie (also known as a Local Shared Object or LSO) is data content that is stored by Adobe Flash on a computer. Although they were originally used to store user preferences and progress for games, they have since become popular alternatives to and used in a similar way to browser cookies as a way to track user’s preferences and behaviour on the web.

Flash cookies have proven to be popular as an alternative to browser cookies because Flash is not actually a part of any browser, but used as an extension. This means that user’s browser preferences regarding internet tracking and cookies have no effect on Flash, since Flash does not save its data to the same directory as a browser does. With users becoming more aware of internet tracking and many disabling cookies, internet trackers use Flash cookies (as well as other methods) which allow them to track internet users regardless of their browser preferences, especially since LSOs can save the same information that would normally be saved by a regular cookie.

An additional privacy concern regarding Flash cookies are their use in cookie respawning, in which deleted browser cookies are rebuilt using data stored in additional locations, such as in Flash cookies.

Additional Information

  • The same LSOs can be used on multiple browsers on the same machine, whilst regular browser cookies are specific to the type of browser that created them.

See Also

Canvas fingerprinting is another internet tracking technique.

Last updated: 22 March 2018