Life-Cycle

elm-pages apps have a different life-cycle than standard Elm applications because they pre-render pages (either at build-time for static routes, or at request-time for server-rendered routes). page

So for example, if you get the window dimensions from the flags and do responsive design based on that, then you'll see a flash after the client-side code takes over since you need to give a value to use at pre-render time (before the app has reached the user's browser so before there are any dimensions available). So that semantics of the flags are not quite intuitive there. So you have to explicitly say how to handle the case where you don't have access to flags.