PADME is a fixed target experiment designed to search for a hypothetical dark photon A' produced in positron-electron annihilations by using a 550 MeV bunched positron beam.
It is expected to be sensitive to the parameter $\epsilon$, describing the mixing between A' and the photon, for $\epsilon > $10$^{-4}$ and for values of the A' mass m$_{A'}\le$23.7 MeV/c$^2$ after about one year of running.
The PADME experiment searches for a dark photon by the missing mass technique in events with only one photon in the final state.
In case of discovery, this technique has the advantage to be not controversial, being a bump above a continuous background of standard electromagnetic processes.
An excellent missing mass resolution is obtained with a high resolution BGO calorimeter,
which is further improved by using a narrow positron beam and an active target to determine the beam position bunch-by-bunch.
An other crucial aspect of PADME is the use of a bunched positron beam to increase the number of positron on target (POT) and improve the search sensitivity.
This choice leads to an increase of events occurring in the same positron bunch which must be disentangled.
The strategy to cope with pile-up events foresees to use fast detectors, to veto on charged particles and small angle photons, to digitize all detector waveforms, by a powerful data acquisition, and to develop robust multi-hit reconstruction algorithms.
This paper illustrates the status of the PADME experiment installed at the Beam Test Facility of Laboratori Nazionali di Frascati after the conclusion of the first data taking period from September 2018 to February 2019.