The iTunes Store is a software-based online digital media store operated by Apple Inc. Opening as the iTunes Music Store on April 28, 2003, it is now the number-one music vendor in the United States. As of January 2009, the store has sold 6 billion songs, accounting for 70% of worldwide online digital music sales and making the service the largest legal music retailer. While most downloaded files have previously included restrictions on their use, enforced by FairPlay, Apple's implementation of digital rights management, iTunes initiated a shift into selling DRM-free music in some countries, marketed as iTunes Plus. On Jan 6, 2009, Apple announced that DRM had been removed from 80% of the entire music catalog in the US. 100% iTunes Plus availability was achieved on 7 April 2009 in the US, coinciding with the introduction of variable pricing, with the removal of songs not available in iTunes Plus from the store altogether.