Twitter is an app and website where logged-in users can post up-to-280-character messages—called "tweets"—and up-to-140-second video/audio messages. These user accounts can like, comment on, and share other users' messages. Some user accounts are "verified" by the company, which bestows special privileges on these accounts, such as more moderation options. Users can choose if they want their profile to be public or private. Anyone without an account can access public tweets but cannot engage with them. The San Francisco-based site was founded in 2006. Twitter is a Casebook value under the "Network Terrain" variable in the code book.