When building Flash apps or games there is very often a need to save some user data. It might be a player's progress in a game or some work done in an application. Usually online application data is being kept in a database and desktop apps are saving to a file on a hard drive. Flash also allows saving to shared objects, so called Flash's cookie files but there is a limit of size set by an operating system and some browsers or anti-viruses may clear them periodically effectively erasing users saved data. While for desktop apps developers choose Adobe AIR, which allows deeper integration with operating systems, not many people know that since Flash Player 10 there is also an option of saving and loading data from a file. In this quick article I will give you a code example of how this feature could be use along with JSON and ByteArrays to effectively save your data to a file.