The total universe of Twitter users and their habits. Also called the "Twitosphere," statistics for the Twittersphere include data such as which days of the week have the heaviest Twitter traffic, and the approximate number of followers Twitter users have; for example, more than half have less than 25, while approximately 5% have more than 250. Obviously, these numbers can change over time. Other measurements of interest are how many people follow multiple tweets and how many tweet writers follow other tweet writers.

The term may also refer less globally; for example, to a personal Twittersphere (those who follow a particular tweet writer), to the Twittersphere of a country or to the Twittersphere of a group, club or other association. See Twitter.