Quantified Self

The Quantified Self is the practice and informal movement of tracking personal data — sleep, heart rate, mood, productivity, biomarkers, glucose, location — as a tool for self-understanding and behaviour change. The phrase was coined in 2007 by Wired editors Gary Wolf and Kevin Kelly to describe a regularly meeting San Francisco group of self-trackers, and it became the umbrella term for the broader movement that followed.

Practitioners range across a wide spectrum. Some are casual users of mainstream wearables (Fitbit, Apple Watch, Garmin) tracking steps and sleep; others run rigorous personal experiments with continuous glucose monitors, EEG headsets, custom data pipelines, and quarterly lab-test panels. The movement's recurring slogan is "self knowledge through numbers". Local Quantified Self meetups follow a distinctive format — three-question presentations ("What did you do? How did you do it? What did you learn?") — that resist commercial pitch and centre lived experience.

The Quantified Self sits inside the broader biohacking movement and shares the conviction that the person being measured should be the primary recipient of the measurement, not merely its subject. That conviction depends on self-custody of data, open-source tooling, and the right to read the formats one's own body emits. The sharpest tension is with the same wearable industry that supplies most of the hardware: many devices ingest data the user cannot export, and a movement nominally about personal sovereignty often runs on infrastructure that maximises corporate access to the same data.