Automatic tool-tips for grid cell text overflow feature is developed in form of plugin. It is listening the ‘afterlayout’ event of the grid and set the tool-tip for cell if no tool-tip exists. If you want to disable overflow tool-tip for particular columns, set the ‘showOverFlowTooltip’ to false. If you will need to change this logic check the ‘GridOverflowTooltipPlugin:isOverFlowTooltipDisabled(column, record, store, view)’ method implementation. The plugin implemented for the latest ExtJS 6.5.3 version.