Photon beam diagnostics at the European XFEL is installed for the control of the FEL beam along specific locations related to the x-ray optical elements, and most of the components are commissioned. Beam diagnostics have to deal with high x-ray beam intensities with the risk of thermal and radiation induced deteriorations. The installation phase started in 2014 in the XTD2 photon tunnel section; SASE1, 2 and 3 are commissioned. Part of the beam diagnostics are imaging devices, for shape, alignment, and pointing of the photon beam. They usually are invasive i.e. the beam is absorbed or partly absorbed, i.e. its properties are partially deteriorated for downstream usage. The FEL pulse intensity is monitored to protect screens from damage $\rightarrow$ Watchdog for screens.