How do i link an app to a database?

I have an app where i can check one of 30 boxes, and it remembers which boxes were checked and loads them back when you open the app again. I have the same app on my pc, how can i link them up so when i check a box on my phone the same box gets checked on the app on my pc?

First question is do you want this to be an online database or local? If local, 30 check boxes isn’t that much so you can just use PlayerPrefs. If you want a “real” database locally, SQLite is the most popular local database.

As far as online databases, if rolling your own then a PHP/MySQL server is a common approach. There are also database as a service providers you can consider, such as Firebase.

Thank you a lot .