What is the best way to save user data on different platforms?

Unity Engine
,
1

I made a game that plan to sale on steam ,android googlePlay and IOS market. For me ,I am not clear what is a standard imlementation
, anyway, I could serialized the gamedata into a txt file or a json file,and what is the best way to synchronized the game data on each platforms,especillay on the moblie platforms. And is there any general method for this?

2

I am not sure whether it is correct to save the data via local device, I am a little doubt about that…

3

The only reliable way is to run your own server and store all the data there.

EDIT: obviously you could use a service such as steam cloud or icloud as well, but the point being that without an external server you control, you cannot compel the user to behave in any particular way to ensure data integrity and consistency across different game instances.

4

I have made a game that on steam platform about two years ago,and at that moment I saved the data into a local file .

Is it common that saved the data on the external server as you mentioned on Steam platform?~

5

I am wanderring is there any open source Unity project that with http server backend for reference?