FlixTraktor

To track which Movies and TV Shows I've seen across multiple platforms, I use trakt, which has integrations with a lot of applications (e.g. Popcorn Time, Plex) but Netflix is not one of them because the lack of an API.

FlixTraktor is a service that uses a headless browser to login to Netflix, get the last watched entries and tries to match them with titles on tMDB. When it find the correct movie of tv show, it marks it as watched at the correct date.