.FCL File Extension
File TypeForeUI Custom Library File
What is an FCL file?
Library file created by ForeUI, a program used to create user interface mockups; saved in a compressed .ZIP format and contains .FCE files, which store custom user-made elements; used for sharing collections of custom elements.
ForeUI custom libraries can be imported using the "Load Elements from .fcl File" option within the Custom Elements pane.