Research　into　photocatalytic　mechanisms　and　charge　carrier　transfer　is　of　vital　significance.　For　type-II　heterostructures　containing　WO3,　a　visualizable　means　is　proposed　for　the　first　time　for　verifying　the　manner　of　charge　transfer　via　observing　the　photochromism　of　WO3.　The　accuracy　of　this　visualizable　means　is　evidenced　through　corresponding　characterization,　such　as　XPS　and　OCP.　In　addition,　photocatalytic　H2　evolution　as　a　supporting　proof　is　studied　to　prove　the　manner　of　charge　transfer　owing　to　the　inactivity　of　WO3.　If　the　charge　transfer　pathway　principally　follows　a　conventional　type-II　manner,　the　heterostructure　will　change　color　from　yellow　to　a　dark　color　and　show　lower　activity　compared　with　the　individuals.　However,　if　the　charge　transfer　primarily　follows　a　Z-scheme　mechanism,　the　color　won＇t　show　a　noticeable　change　but　much　higher　activity　will　be　exhibited　than　that　by　the　individual　components.　CdS-WO3　and　ZnIn2S4-WO3　(ZIS-WO3)　are　used　as　examples　to　verify　the　universality　of　this　method　and　exclude　the　impact　of　the　crystal　phase　of　WO3　on　photochromism.　©　The　Royal　Society　of　Chemistry.