Quantified self refers both to the cultural phenomenon of self-tracking with technology and to a community of users and makers of self-tracking tools who share an interest in "self-knowledge through numbers". Quantified self practices overlap with the practice of lifelogging and other trends that incorporate technology and data acquisition into daily life, often with the goal of improving physical, mental, and emotional performance. The widespread adoption in recent years of wearable fitness and sleep trackers such as the Fitbit or the Apple Watch, combined with the increased presence of Internet of things in healthcare and in exercise equipment, have made self-tracking accessible to a large segment of the population.

A lifelog is a personal record of one's daily life in a varying amount of detail, for a variety of purposes. The record contains a comprehensive dataset of a human's activities. The data could be used to increase knowledge about how people live their lives. In recent years, some lifelog data has been automatically captured by wearable technology or mobile devices. People who keep lifelogs about themselves are known as lifeloggers.