A filter bubble is a state of intellectual isolation that arises when personalized searches, recommendation systems, and algorithmic curation selectively presents information to each user. The search results are based on information about the user, such as their location, past click-behavior, and search history. As a result, users are increasingly exposed to information that reinforces their existing beliefs, while also separating themselves from content that challenges them. This has effectively enclosed individuals in a cultural or ideological bubble, resulting in a narrow and more customized view of the world. The choices made by these algorithms are only sometimes transparent. Prime examples include Google Personalized Search results and Facebook's personalized news-stream.