NFA, Netflix Audio File (.nfa)
The NFA Audio file format
Netflix is popular for streaming many different TV series and movies that are, in part, not aired on TV anymore, as well as comedy specials, documentaries and original content produced by Netflix. Since December 2016, the mobile app for both Android and iOS also offers the possibility to watch Netflix offline. In order to watch Netflix offline, data has to be stored on the user’s device, such as the video and subtitle data, but also the audio data. This is what Netflix developed the NFA file for, to store the audio streams of downloaded content onto the device.
Technical details of NFA files
In order to allow users to watch Netflix shows and movies offline, the streaming service had to find a secure way to store data for these videos on the user’s device. For this, Netflix developed a set of encrypted files that are referenced by the Netflix app when watching offline content. NFA is one of these files, responsible for storing the audio data of the downloaded episodes or movies. In essence, NFA files are MPEG-2 Advanced Audio Coding files (AAC) with a different file extension. These Netflix audio files are stored in the same folder as the other files that are needed for the Netflix app to be used without an internet connection. This includes, among others, NFV, NFS and NFI files.