The basic MP3 decoding and encoding technology is patent-free in the European Union, all patents having expired there. In the United States, the technology will be substantially patent-free on 31 December 2017 (see below). The majority of MP3 patents expired in the US between 2007 and 2015.
Where is the basic MP3 decoding and technology patent free? What happened to the patents that caused them to be patent-free? When will the technology be patent - free in the United States? Between which years did most of the MP3 patents in the US expire?