Web check-in has become a standard feature for most airlines, but for budget carriers in Asia, it is often a mandatory step that can save you time and money, or cost you extra if you skip it. Understanding each airline's web check-in window, fees, and requirements is essential for a smooth journey at the airport. This guide covers the web check-in policies of five major low-cost carriers operating in and from Singapore: Scoot, Jetstar Asia, AirAsia, Cebu Pacific, and VietJet. We explain deadlines, fees, baggage implications, seat selection, and what happens if you do not check in online.