You can use view formatting to customize how items in SharePoint lists and libraries are displayed. To do this, you construct a JSON object that describes the elements that are displayed when an item is loaded in a view and any styles to be applied to those elements. View formatting does not change the data in list items; it only changes how they're displayed to users who browse the list. Anyone who can create and manage views in a list can use view formatting to configure how views are displayed
To open the view formatting pane, open the view dropdown and choose Format current view.