Netflix reveals how it classifies viewers to track show performance

Netflix has detailed how it evaluates the performance of TV shows and movies based on how long the content is watched and, in the case of TV shows, how many episodes are streamed. The details were revealed in a letter the company sent to the UK Parliament, which published the note online as part of its probe into on-demand video services. According to the letter, Netflix splits content up into three categories.

Netflix has historically kept its viewership information a secret — at least from the public — though there have been some instances in which the company published numbers to brag about an achievement. In the newly published letter, the public has learned how Netflix evaluates a show or movie's performance in order to share that information with its partners.

The company evaluates content based on the number of households that watch it, the first category of which is 'starters,' a term referring to households that watch two minutes of a movie or episode in a series. Beyond that, the company has a 'watchers' category, which it considers households that watch 70-percent of a movie or one whole episode of a series.

The third category is called 'completers,' which refers to households that watch 90-percent of a movie or TV show season. These viewing metrics are determined seven days and 28 days after the content arrives on Netflix. The company says its 'watchers' details are 'selectively' shared with creators and the public.

These metrics are used in North America and Europe, according to the letter; Netflix states it may share these details with partners in other countries. Household numbers are the metric Netflix has used to brag in the past — for example, the company said that 64 million member households watched the third season of Stranger Things in its first month.