Do I need to file my taxes online today if I am asking for an extension from the feds and owe the state nothing?

For a majority of states, you get an automatic extension when you file a Federal one - some give you an automatic extension regardless - and some require a separate one.  Consult the article below for information pertaining to your state.

https://ttlc.intuit.com/questions/3931162-does-my-federal-extension-apply-to-my-state-taxes