When something lets you cast something at will, do you cast it as an action or is it free?

@JeremyECrawford When something lets you cast something at will (e.g. Eld Invocations), do you cast it as an action or is it free? #DnD

— Atezca (@Atezca25) May 17, 2017

Being able to cast a spell at will means it doesn't cost a spell slot. That ability has no effect on the spell's casting time. #DnD https://t.co/ZTDCnHB9xu

— Jeremy Crawford (@JeremyECrawford) May 17, 2017

@Atezca25 You're welcome!

— Jeremy Crawford (@JeremyECrawford) May 17, 2017