MAL Updater keeps your MyAnimeList.net anime list in step with what you are actually watching. It has been maintained since 2007, it is free, and it is a single portable executable.
What it does
- Watches your media player and works out which episode of which series is playing.
- Updates the matching entry on your MyAnimeList account.
- Stays out of the way otherwise — no account of its own, no background service.