Heads up, Creators: On Dec 13-14 you may see a noticeable decrease in your sub count as we remove spam subscriptions. If spam is removed, you'll see a YouTube Studio alert: https://goo.gl/qGDBvX This should help give you confidence that the subs you do have are real fans!
Spam subs includes fake/artificial means of subscription. We use technology to identify such accounts & we don't remove legit subscribers. Also, if you're subscribed to a channel & you haven't watched in a while, you'll still be subscribed. This update only removes spam accounts.