can people use the paid app in multiple devices?

I would suggest that you (your company) think of your customers as users instead of devices. If I subscribe to your service, then why does it matter if I use it on my iPhone or my iPad? I am not going to give my Apple ID to anyone else, as that is similar to a blank cheque: they could then spend my money, if they had that information. And other account related worries (email, account blocking, mischief).

Even MDM devices have each their employee Apple ID, not lumped all on one account.

ilker142 wrote:

Thank you.

In my conutry, some people fraud about this issues. one apple id, one subscription, over fifty different devices are using the same subscription,

is there any device limit for this type issues?

Copy Protection schemes will always fail and will always be bypassed, which means the goal here is not so much to prevent all misuse (which won’t be possible) but rather to do the minimum work of enforcement while also avoiding causing licensing hassles for the folks that are actually paying for your app or your service.

Read the Apple EULAs, as a starting point for what Apple has implemented.

Legal - Software License Agreements - Apple

Here’s the general summary: up to ten copies, of which up to five can be computers: View and remove your devices that are associated with Apple ID purchases - Apple Support

Family Sharing allows sharing purchases up to six people, if enabled for both the Apple ID and the app.

You’re also going to need to create your own EULA: Apple Developer Documentation

You’ll also find more to read in Apple’s App Store Connect website.

ilker142 wrote:

4. can other iphones still benefit from this subscription even while x apple id is log out.

It depends on how you implement it. This can get complicated in a hurry.

Apple does have solutions for this. Review the DeviceCheck documentation.

Apple is hosting some App Store Connect technical sessions right now: https://developer.apple.com/events/view/upcoming-events

And you always have the option to use a DTS ticket to ask for support directly from Apple.

In all honesty, you should consider how much exposure you have. Are you incurring any costs (other than lost revenue) from fraudulent behaviour? If not, then the effort you put into to stop it is going to be an expense. But if you have to pay for that yourself, then you will want to more carefully manage it and things like DeviceCheck and server-to-server subscription notifications might be appropriate. Also, consider when you need to do this work.

If you are just starting out, it may be more important to have more users. Get companies hooked on your services, then implement more strict device checking later. They may not have paid initially, but they might have to pay more just to maintain their access, even temporarily. So a little bit of early-adopter piracy might be beneficial in the long run. Just keep an eye on your own costs.

ilker142 wrote:

i wonder that if people log in multiple devices with same apple id, can they use our paid app in multiple devices without paying for every devices? and if yes, how can we avoid from this issue?

Yes. You can't avoid it. That is a feature. If this were possible, how would people even manage these subscriptions?

You can, however, prevent people from using Family Sharing. I think the default for Family Sharing support is OFF, but you should probably double-check that.

ilker142 wrote:

But there is a possibility for fraud. one apple id, one subscription, one hundred different devices are using the same subscription? is it possible or is there any device limit?

Please see MrHoffman's post above for links to Apple Support documents that show the limitations on the number of devices that can be used with a single Apple ID.

The only thing I can add is that this is Apple's system and Apple makes the rules. You are the wholesaler and Apple is the retailer.

Your best defence against fraud is to stay in Apple's system and correctly implement Apple's licensing. It is your responsibility to do that. If you do it wrong, then you could have hundreds of different devices using a single subscription. I am one of the few people to have attempted the same app both inside Apple's system and outside. I can assure you that protecting your app against piracy and other illegal acts is much easier inside Apple's system. It isn't easy, but it is much easier than trying to do it yourself.

ilker142 wrote:

one last question..

You are asking the question already answered.

Apple subscriptions are associated with Apple IDs.

Not with devices.

Apple app purchases, and Apple subscriptions, are associated with an Apple ID.

Apple app purchases and Apple subscriptions are not transferable among Apple IDs, though can be shared among Apple IDs when both the Apple ID is configured for Family Sharing and when the app is enabled for Family Sharing.

Up to ten devices, five of which can be computers, are permitted to be logged in per Apple ID.

All licensing schemes can be cracked.

And as mentioned, developers can also mis-implement the Apple licensing checks.

If you do decide create your own licensing scheme outside of the Apple subscriptions, well, you’re not only going to have to do that ~perfectly, you’re also going to have to uniquely identify an iPhone and while Apple is seeking to better anonymize that information to reduce tracking, and you’re going to have to get your subscription scheme past Apple app review. Whether your licensing scheme also merely serves to annoy your paying customers is another and oft-overlooked factor here, too.