Our custom content is made completely optional for all players. No one ever downloads a single content file for custom items when they connect.
Because the content is optional, we have made sure that players who have not installed the content pack can play normally without any issues by not playing custom sounds and rendering custom sprites for these players.
For players who have installed the content pack, the content distributor would have notified our data center that they had installed, and we will enable playing custom sounds and rendering of custom sprites to them.
When a new content update is released, the servers will automatically disable hearing and seeing custom content for you.
When you use a custom item, the server will notify you that your content pack is outdated.