Glass defects are always undesired because of their significant costs to manufacturing industries. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is a versatile technique for local trace element analysis in a wide variety of solid samples. Furthermore, the coupling of laser systems to double-focusing sector field mass analyzers provides low limits of detection with a high mass resolving power, allowing the accurate analysis of P, S and Cl traces in local defects of coated glasses. Three different types of defects, depending on the impurities identified at the LA-ICP-MS profiles, were found in the selected coated glasses (with metallic and oxide films in the low nanometre range), enabling the unambiguous identification of the contamination source that produces the local defects.