Nick here from Shopify. Great question!
Private apps in a Shopify store admin are generally easy to detect as there are usually no support links present and I think a warning message is also displayed. You can see what private apps are installed on a store by going to Apps > Manage private apps in the admin. There is a help guide Shopify has for this which might be useful that you can see here.
In terms of whether or not they are in use. as long as they are visible on that Manage private apps page they could be potentially in use. There is no on or off switch for example, but this is a great indication they are in use if they are here. They can be deleted off that page and therefore off of the admin. You can't really see what the app is actually doing- what it is showing is that there's a connection open between this store and an external app.
I hope this helps and answers your question!
All the best, Nick
Thanks Nick. Yeah I had read through all the documentation and sorta figured what you mentioned.
It would be extremely helpful to have some insight into private apps. I can't just turn them off as something unknown to me may break. Yet I cannot upgrade the API endpoints because I'm unsure where they are used. I can't even temporarily turn them off, see the consequences, and turn back on. The joys of inheriting software.
I was hoping the API Health Dahsboard would help, but it doesn't cover private apps.
No problem at all @marcpeterson.
If it's at all possible you should try to get in contact with the developers who set up the private apps to determine which are crucial to the store, and which, if any can be removed without causing disruption. Once a private app is created, the info which can be captured on the admin is limited- this is the current disadvantage of working with private apps. I wish I could help you more or there was a more direct way to see private apps in use but contacting the developer if possible would be the best way for now.
While this might not help you exactly with the situation you are in right now but it might be good to have it going forward. But Shopify introduced custom apps as an option for safer, more robust integrations for single stores. You can see the guide for that here and the blog post with some more details here.