Using Twitter as a case study, this article hypothesizes that social media content that is produced on mobile versus web platforms may be qualitatively different. As we increasingly tweet from our smartphones, we may be encouraged to “report” on our immediate thoughts, feelings, physical self, and surroundings. This article seeks to understand whether these presentations of self tend to be more egocentric, negative/positive, gendered, or communal depending on whether they were tweeted from mobile devices or web platforms. Using 6 weeks of Twitter data collected in 2013, we found evidence that users tweet differently from mobile devices and that mobile tweeting is informing new behaviors, attitudes, and linguistic styles online.