https://www.techradar.com/news/netflixs-new-smart-downloads-will-keep-pace-with-your-binging-habits

Netflix has unveiled a new feature today that will help you better manage your downloaded TV series. 

The feature, which will be exclusive to Android devices at launch, is appropriately called ‘smart downloads’ and its purpose is to delete any episode you’ve already watched, plus automatically download the next episode in the series the next time you’re connected to Wi-Fi - i.e. if you download the first episode of Stranger Things and watch it, smart downloads will delete that first episode and download the second automatically next time you're connected to Wi-Fi.