A Flash cookie, also known as a local shared object, is a text file that is sent by a Web server to a client when the browser requests content supported by Adobe Flash, a popular browser plug-in.
Flash cookies are commonly used in website advertisements and videos. Like HTTP cookies, Flash cookies store information on the end user's computer. The information allows a website to recognize the client's browser when it returns. Flash cookies sometimes contain the same information that HTTP cookies contain, but they also store information specific to Flash such as the place where the user's video stopped playing or an animated banner advertisement stopped rotating. Local shared object files have an .sol file extension.
To deal with potential abuses of local shared objects, Adobe has made changes in Flash to discourage Flash cookie respawning and has provided information on their website about Flash cookie management. The company has also partnered with major browsers to make it possible for end users to manage local shared object files through browser settings with an additional application program interface (API).