The ability to detect motion and track a moving object hidden around a corner or behind a wall provides a crucial advantage when physically going around the obstacle is impossible or dangerous. Previous methods have demonstrated that is possible to reconstruct the shape of an object hidden from view. However, these methods do not enable the tracking of movement in real-time. We demonstrate a compact non-line-of-sight laser ranging technology that relies upon the ability to send light around an obstacle using a scattering floor and to detect the return signal from a hidden object with only a few seconds acquisition time. By detecting this signal with a single-photon avalanche diode (SPAD) camera, we follow the movement of an object located a meter away from the camera with centimetre precision. We discuss the possibility of applying this technology to a variety of real-life situations in the 1 near future.Recent years have seen remarkable advances in the field of image processing and data acquisition, allowing for a range of novel applications [1][2][3][4][5][6][7][8]. An exciting new avenue is using optical imaging techniques to observe and track objects that are both in movement and hidden from the direct line-of-sight. The ability to detect motion and track a moving object hidden from view would provide a crucial advantage when physically going around the obstacle is impossible or dangerous, for example to detect a person moving behind a wall or a car approaching from behind a blind corner.Techniques for imaging static objects that are hidden from view have been recently demonstrated relying on, for example, radar technology [9,10], variations of laser illuminated detection and ranging (LIDAR) [3,5,11,12], or speckle-based imaging. The latter approach was first developed for imaging through opaque barriers [13][14][15], and also allows for imaging around corners [16,17]. The work of Velten et al. [5] and, more recently, Buttafava et al. [8] sets out to establish the 3D shape of a static hidden object by collecting the return scattered light with a streak camera or single-photon avalanche diode, respectively. While remarkable 3D reconstruction of objects are achieved with these techniques, Buttafava et al. point out that the requirement for scanning and subsequent long acquisition times mean that their technique is currently unsuitable for imaging moving objects.Notwithstanding these ingenious imaging systems, locating the position of a hidden object in motion and monitoring its movement in real time remains to date a major challenge. We set out to solve the tracking problem and develop a technique based on both hardware and software implementations that are specifically designed for this 2 purpose. Our solution is based on a LIDAR-like approach where a single-photon avalanche diode (SPAD) camera [7,[18][19][20][21][22] is used to image light that is backscattered from beyond the direct line-of-sight (see Methods for camera details). The high temporal resolution of the camera relies on the fact that each indiv...