The official docs have a good guide about this: JSON serialization is a very mundane task. Why does the USA not have a constitutional court? As you can see I am using Firebase Cloud Functions to return a data with nested data objects, and I struggle to get them serialized. It is recommended to install plugins for your code editor. How to parse List of objects from firebase realtime database Flutter, type '_InternalLinkedHashMap
' is not a subtype of type 'List