Annict is a web service for anime fans.
You can track episodes and discover anime.
You can track episodes to prevent "What episode did I watched?". And you can also write a comment each episodes as you like.
You can set a state (Plan to Watch, Watching, Completed, On Hold and Dropped) to anime.
You can see your anime list on profile page, and you can also check your activity graph.
Annict is a social network. So you can follow your friends on here. Their activity are displayed on your timeline.
When friends post a comment about an episode, it will be blurred if you have not watched it. This feature protects you from spoiler.