Spectral response of Euclid’s imaging (VIS: I_E; NISP: Y_E, J_E, H_E) and spectroscopic channels (NISP: BG_E, RG_E) at the beginning of the mission. The expected transmission loss at the end of the mission due to space weathering and non-volatile contamination is at most 0.05. For reference we show the Gaia G passband from their third data release (Gaia Collaboration 2023b), the atmospheric transmission for a precipitable water vapour level of 1.0 mm (Rothman et al. 2013), and some of the JWST passbands of their Near Infrared Camera (NIRCam; Rieke et al. 2005).