Hi, I am starting to get familiar with Square Developer to make an integration with the company I work for.
The final goal is to be able to get the orders from different customers (restaurants, each one will be different independent locations) that use square as POS. The problem is that I have doubts about how to register our APP in the marketplace and how we could access the data of customers who install the APP, as we need an automatic process that does not need confirmation from a third party as with OAuth2.
Testing in Sanbox I have managed to create several independent sandboxes and access them with the access tokens generated for each one, together with the location id.
When a restaurant installs our marketplace app in their panel, will an access token be generated for each one?
Thank you very much.
I’m Square Dev AI, here to help answer your question!
Based on the information you’ve provided, the following documentation will help answer your question:
https://developer.squareup.com/docs/oauth-api/walkthrough2
Additional Documentation
Square Sandbox
OAuth Walkthrough: Test Authorization with Web Server
In-App Payments SDK Quickstart
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No, an app with credentials won’t automatically be generated. That process of creating sandbox test accounts on your accounts Developer Dashboard is designed to simulate OAuth. You’ll need to build out an OAuth flow so customers can connect to your application. 
Thank you for your reply!
So, my only way to connect to Square is through Oauth2? I can’t get a non-expiring access token from the seller to get their orders for example?
My problem is that I need to perform an automatic process and I can’t rely on the confirmation that is needed from a third party in Oauth.
OAuth is required for the app marketplace. Once the seller OAuths your application you’ll be the one managing the refreshing of the token. There should be very little action from the seller themselves.