Low energy photons, from radio frequencies to gamma rays, have always been the most privileged messengers to explore the Universe. At ultra-high energy, above 10$^{18}$~eV, photons are predicted in many scenarios explaining the origin and the propagation of cosmic rays. The observation of such photons would have a significant impact on several research fields, from astrophysics to fundamental particle physics. Giant air showers experiments are unique tools to search for ultra-high energy photons. An overview of the detection techniques and of the latest experimental results is presented.