A respawning cookie is a standard HTTP cookie backed up by data stored in additional files that are used to rebuild the original cookie when the user visits the originating site again.
There are a couple of methods used to create respawning cookies. Flash cookies, also known as local storage objects (LSO) can be used to create a duplicated tracking record from which the original cookie is rebuilt. Flash cookies are less known and more hidden in the operating system than regular HTTP cookies. As a result, they are less frequently deleted. Because Flash cookies lack an expiration date and have a much larger file size (100KB max versus HTTP cookies 4K), they can be exploited to indefinitely store the tracking info that would be lost in the denied or deleted cookies while also storing much more information.
HTML5 local storage and cache cookies through entity tags (ETags) are another method used to respawn HTTP cookies. ETags can store the same info as HTTP cookies. Again, the sites recognize the PIE and use covert backup to enable reconstitution of the cookie data.
Either of these methods offer members of a consumer tracking firm’s subscriber base more complete information about consumer comings and goings and, thus, interests that can inform marketing efforts.
Newer versions of Flash include options to delete the info required for respawning cookies. Previously, third-party utilities were required to remove them.
The term respawning comes from multiplayer first-person shooter computer games. In these games, when your character dies, you can usually hit a key to restart and have the character “respawn” and reappear in another location.