There are three ways in which you can check in at the Qatar Airways-Web, Mobile and at the Airport.
Online check in has different time restrictions for the to/from US flight and the non-US flights. For the flights departing to US from Doha and for flights from US, the online check in opens 24 hours before the scheduled departure of the flights. For all other flights, the online check in is available from 36 hours and up to 90 minutes before the scheduled departure. This type of check in can be used on all flights operated by Qatar Airways but is not allowed for passengers from Baghdad, Salalah, Mashhad, Basra or Shiraz. If you are carrying the checked in baggage, then the same has to be checked in at the airport. With online check in facility, you are able to choose your seat and get the printed format of the boarding pass.
Mobile Check in is another method for the convenience of the passengers. This can be done by using the mobile phone application of the Qatar Airways. This is available both for Android and iPhones.
Airport Check in is available 3 hours prior to departure and the closing time is different for the economy and the first and business class passengers. For the Economy class travelers, the check in at airport closes 1 hours before the departure time and for the other two classes of passengers, it is 45 minutes.
Priority check in facility is provided for the Silver, Gold and Platinum members.