The file doesn't need to be uploaded for it to be edited within a web app – everything can be 100% local, including saving editor state (through local-storage).

The file doesn't need to be uploaded for it to be edited within a web app – everything can be 100% local, including saving editor state (through local-storage). The only network access absolutely necessary is downloading the web app code initially but after first load it's possible for a web app to work offline