Netflix Starts Using VP9 Codec, Saving Up to 36% of Bandwidth 

One of the biggest differences between shows you download and shows you stream on Netflix is the video format, or codec, the company is using. For streaming, Netflix has been using H.264/AVC almost exclusively. However, users who download Netflix shows to most Android devices instead receive content encoded with VP9.

Source: Netflix Starts Using VP9 Codec, Saving Up to 36% of Bandwidth | Variety