The UK Singles Downloads Chart is a weekly music chart that ranks most-downloaded songs in the United Kingdom over the past seven days. It is compiled by the Official Charts Company on behalf of the British music industry, and is based solely on non-subscription downloads of songs from official music retailers. The chart was founded in 2004 and was first published on 1 September that year. The first artist ever to reach number one was Irish boy band Westlife. Since then, as of 13 April 2013, 200 different artists have reached number-one on the UK Singles Downloads Chart as either a main or featured artist. The following table lists those artists. The totals do not include non-credited appearances (such as those on multiple-artist charity ensembles), although they are .