the uk albums chart is a music chart compiled by the official charts company (occ) that calculates the best-selling artist albums of the week in the united kingdom. since 2005, the chart has been based on the sales of both physical and digital albums, on the condition that the album was available in both formats. in january 2007, the rules were changed so that legal downloads of all albums, irrespective of whether a physical copy was available, were eligible to chart. further changes occurred in february 2015 when audio streaming was included for the first time.