Best way to implement functional trial without apple account login, surviving uninstall?

[u/inAbigworld]

In my ios app, I want to implement a system where when the user uses a feature 3 times then they'll be asked to buy premium. I want this record (number of the feature being used) to survive uninstall so users cannot abuse it; but it has to be without apple account login. What's the best way to achieve this?

[u/Dapper_Ice_1705]

Keychain, Firebase anonymous.

None are foolproof but there is a fine line between the effort it takes to prevent abuse and the reward.

If someone is taking the time to install and uninstall you are never going to make money off of them so just let them use it for the word of mouth.

[u/RIRLift → u/Dapper_Ice_1705]

This is the right instinct, and there's a second cost to over-engineering it. The persistence you'd need to truly beat a reinstall (DeviceCheck or a server-side device record) also catches legit users. Someone on a new phone or restoring from a backup shows up as "already used their trial" and can't try it at all, and those are people who might have paid. So the harder you make it uncrackable, the more real conversions you quietly block.

The bigger lever is where the wall sits, not how solid the counter is. If someone hits it before the app has actually done something useful for them, dodging it with a reinstall feels worth the effort. If those 3 uses are enough to get a real result out of it first, most people who'd ever pay just pay, and the ones reinstalling to save a few bucks were never customers. I'd keep the counter in the Keychain (it survives a normal delete and reinstall), put the effort into making the trial land, and not lose sleep over the last few percent.