HILIGT - an upper limit and flux server for photon-counting instruments. The advent of all-sky facilities, such as Swift, ASASSN, eRosita and LSST has led to a new appreciation of the importance of transient sources in solving outstanding astrophysical questions. Identification and catalogue follow-up of transients has been eased over the last two decades by the Virtual Observatory but we still lack a tool to provide a seamless, self-consistent, analysis of all observations made of a particular object by current and historical facilities. HILIGT is a web-based interface which polls individual servers, written for the XMM-Newton, Integral and other missions, to find the fluxes, or upper limits, from all observations made of a given target. These measurements are displayed as a table or a time series plot.