Abstract Raman spectra of (MY) _x (Ga₂S₃)_0.2−0.2x (GeS₂)_0.8−0.8x pseudo-ternary glassy systems (M = Na, K, Rb; Y = Cl, Br, I) were investigated systematically as a function of MY nature and alkali content. Raman spectroscopy of the Ga₃S₃-GeS₂ glassy matrix shows a complicated local structure: corner-sharing CS- and edge-sharing ES-GeS_4/2 tetrahedra, Ga-S triclusters and ETH-Ga₂S_6/2 ethane-like units. The Ga₂S_6/2 population decreases with increasing x related to a substitution of some bridging sulfur atoms around central Ga by terminal Y species with a respective decrease of the network rigidity. The formation of mixed Ga-(S,Y) environment is affected by the M⁺ ion size and the MY concentration.