Purpose This paper aims to fill this gap by providing a conceptual framework for discussing “technologies of the self and other,” by showing that, in most cases, self-tracking also involves other-tracking. Design/methodology/approach In so doing, we draw upon Foucault’s “technologies of the self” and present-day literature on self-tracking technologies. We elaborate on two cases and practical domains to illustrate and discuss this mutual process: first, the quantified workplace; and second, quantification by wearables in a non-clinical and self-initiated context. Findings The (...) main conclusion is that these shapings are never neutral and have ethical implications, such as regarding “quantified otherness,” a notion we propose to point at the risk that the other could become an object of examination and competition. Originality/value Although there is ample literature on the quantified self, considerably less attention is given to how the relation with the other is being shaped by self-tracking technologies that allow data sharing. (shrink)