1 Self-Tracking Deborah Lupton Preprint version of an essay written for Information: Keywords, edited by Samuel Frederick, Michele Kennerly and Jonathan Abel, to be published by Columbia University Press. Introduction Self-tracking is a form of personal knowledge creation. The term ‘personal informatics’ is sometimes used to describe this process, particularly by researchers in computer science. A recent community of self-tracking enthusiasts employ ‘the quantified self’ to describe their activities. ‘Lifelogging’ is a variant of self-tracking that received attention for a while before the quantified self largely replaced it. I define self-tracking as a reflexive mode of practice that is adopted by people as a way of learning more about themselves by noticing and recording aspects of their lives, and then using the information that is gathered to reflect on and make sense of this information. Self-tracking is often undertaken as a way of optimising or improving life in some way. It can also simply involve using personal information to engage in a process of self-discovery, self-awareness and supplementing memory. Some self- trackers keep their personal data to themselves as a private practice: others choose to share their information. Almost any aspect of life can be tracked, from bodily functions and activities to work performance, finances, energy consumption, sexual encounters and moods. Self-tracking may be simply a mental strategy – a mode of self-awareness, in which individuals take care to notice specific features of their lives and make mental notes and comparisons. Alternatively, a raft of technologies may be used to collect and store this information, from the time- honoured paper-and-pen method (as in journal writing), to the recent digital tools of mobile cameras, computer spreadsheets, online platforms, mobile apps, wearable devices, and even insertable or ingestible devices that go inside the human body. It is on these novel forms of self-tracking, and the digitised forms of information generated from them, that I focus in this essay. While people have engaged in tracking and recording aspects of their bodies and lives since antiquity, new digital technologies provide opportunities to accomplish these activities in unprecedented ways. Many of the devices and software designed for self-tracking are partly or fully autonomised, and generate data throughout the day (and in some cases, during sleep). Digital cameras in mobile or wearable devices facilitate image-taking that records elements of a person’s life. Social media platforms can also produce personal information: how many friends or followers a person has, how other users respond to the content a person uploads, and so on. Productivity apps and platforms monitor how people spend their time. Some self-tracking technologies use digital sensors, which can monitor a wide range of bodily functions and activities that were previously not readily detected or recorded by the human senses. These include steps taken, heart rate, stress levels, energy expended, food and liquids consumed and sleep patterns. Smartphones with tracking apps are carried on or strapped to the body. Wearable devices such as smartwatches and ‘smart’ wristbands, ankle bands, headbands, gloves, pendants, rings, clothing and footwear with digital sensors are