Adding a day?

[disneyduonj]

Hi,
I know I can add a day at guest services once I am there, but can I add a day online before we get there so I can do Fast Passes in advance? I bought a 4 day (no hoppers) ticket and want to make it a 5 day (no hopper).
thanks!

 

[DisneyWishes14]

If it's part of a package, yes. If you purchased the tickets separately, no.