The structural changes of charged-discharged crystalline WO3 films have been studied using ex-situ IR spectroelectrochemical measurements. The films were deposited on transparent conducting glass (F:SnO2, Flabeg) and Si wafers by dip coating from a peroxopolytungstic acid solution. Annealing was then performed at 150 and 300 degreesC (60 min) and at 500 degreesC (15 min). At 150 degreesC, an amorphous WO3. nH(2)O phase forms while annealing at 500 degreesC produces a monoclinic WO3 (m-WO3) modification. XRD and IR spectroscopies were used to assess the film structure and crystallinity. Crystalline films were galvanostatically charged-discharged to a different level of insertion coefficient (x) in 0.1 M HClO4(aq), 1 M LiClO4/propylene carbonate (PC) and 1 M NaClO4/PC electrolytes. Ex-situ IR spectra of all intercalated films exhibit a pronounced increase in absorption between 8000-1000 cm(-1) due to the quasi-free electrons. We observed differences between the IR spectra of WO3 when charged to varying levels of x with H+, Li+ and Na+. The intercalation of m-WO3 independently of the inserted ion leads to the transformation from monoclinic to tetragonal and further to cubic phase. By using site symmetry group analysis we predicted the number of IR and Raman active W-O stretching vibrations for HxWO3, LixWO3 and NaxWO3 in cubic, tetragonal and monoclinic phases. We observed a single W-O stretching for the c-LixWO3 (Pm3m) and two for the c-HxWO3 (Im3) phase, which agrees with the lowering of the site symmetry of WO6 groups in the latter phase. For the t-HxWO3 and t-LixWO3 films, a similarity between the corresponding IR spectra indicates that the structure of the tetragonal phases does not differ significantly.