You can track animes you watched so that you don't get "How many episodes did you watch?".
You can white an impression on the record, and later you can look back on what you thought at that time.
You can manage animes with 5 viewing statuses: "Watching", "Plan to Watch", "Watched", "On Hold", and "Stop Watching".
Animes with each status can be listed on your library page.
When you follow an Annict user, the viewing record of that person will be displayed on your timeline.
To prevent spoilers, comments of animes and episodes that you haven't seen are blurred.
Annict publishes Web API that allows you to obtain anime data and your own viewing data.
You can use the Web API to create anime-related applications or create your own Annict client.