There are numerous websites that list the top 10 songs, but some differ in criteria used to determine which songs are in the top 10. Some websites that list the most popular or most downloaded songs are Billboard.com, Top10Songs.com and iTunes.
Some websites such as Billboard.com determine the top 10 songs based on Nielsen Music's measurements of sales data and radio airplay audience impressions. Top10Songs.com and some other websites use information from online music retailers to base their rankings on the most frequently downloaded and streamed songs. Billboard.com, Top10Songs.com and iTunes all let visitors see top 10 charts from previous weeks, months and years.