Every time I uninstall and install my app, a new identifierForVendor is generated.
I found out that it is an ongoing issue of Apple.
My follow-up question is, will it then be possible for two or more devices to have the same identifierForVendor if they keep uninstalling・reinstalling?
Teoretically yes, but for practical applications you shouldn’t need to worry about this.
identifierForVendor is of UUID type - this wiki page has a section on collision probability for UUIDs in general, not only on iOS. The short of it is that in order to have 50% chance of collision you’d need to generate ~2.71*10^18 identifiers. And thats
equivalent to generating 1 billion UUIDs per second for about 85 years. A file containing this many UUIDs, at 16 bytes per UUID, would be about 45 exabytes.
Also, I wouldn’t say that its an „issue”, but rather a decision choice made by Apple - in the documentation they clearly state that
The value in this property remains the same while the app (or another app from the same vendor) is installed on the iOS device. The value changes when the user deletes all of that vendor’s apps from the device and subsequently reinstalls one or more of them. The value can also change when installing test builds using Xcode or when installing an app on a device using ad-hoc distribution. Therefore, if your app stores the value of this property anywhere, you should gracefully handle situations where the identifier changes.
Related
Before Swift 2.2 the UUID value was the same every time I opened the app, now changes at every opening
I use this code:
UIDevice.currentDevice().identifierForVendor!.UUIDString
How can I do now to identify the user?
Every time you delete the app, the UUID may change.
If you just close and open the app, it's should be the same.
But if you delete the app (or install it again via xcode), it might change.
There are a couple of answers that explain why the UUID is resetting. There's one that offers a potential work around, but I'd consider it far from ideal. But I want to highlight something important about the way UUID's work that serves as a great workaround that has absolutely zero impact on the production OR debug version of your code base or compiled binary.
The value in this property remains the same while the app (or another app from the same vendor) is installed on the iOS device. The value changes when the user deletes all of that vendor’s apps from the device and subsequently reinstalls one or more of them.
All you have to do to prevent this value from changing while developing App-A is to simply install App-B from the same vendor (yourself) and keep it installed during the life time of App-A's development. This is literally as simple as starting a blank new iOS project and install the blank slate to your test device (using the same developer account & such), and then never uninstall it again during development.
App-B keeps a constant UUID for the vendor (yourself) so no matter how many times you delete and reinstall App-A, it will always keep the same UUID.
This actually seems to be a bug IMO. Everytime I run my app in the simulator it generates a new Vendor ID. You can probably get round it by storing the ID into NSUserDefaults on the first bootup then retrieving / comparing the value from NSUserDefaults instead of getting it from identifierForVendor. This will save a static vendor id in defaults but in theory the vendor id will still be changing every boot up.
Kind Regards,
Krivvenz.
Update: I can confirm I have installed multiple apps on the same simulator too but the vendor ID is still changing on every boot.
Update 2: - I have logged this as a bug with Apple - 26195931.
The value of this property is the same for apps that come from the
same vendor running on the same device. A different value is returned
for apps on the same device that come from different vendors, and for
apps on different devices regardless of vendor.
The value in this property remains the same while the app (or another
app from the same vendor) is installed on the iOS device. The value
changes when the user deletes all of that vendor’s apps from the
device and subsequently reinstalls one or more of them. The value can
also change when installing test builds using Xcode or when installing
an app on a device using ad-hoc distribution. Therefore, if your app
stores the value of this property anywhere, you should gracefully
handle situations where the identifier changes.
Refer this link for more info.
I'm aware if the following methods, each which has it'd flaws
UDID
Advertising Identifier
Vendor ID
The problem with UDID is that its deprecated and doesn't even work as of ios7, problem with other two is that the user can change them via software reset of phone or reinstallation of app
Another interesting solution I found is to randomly generate one yourself and then save to keychain to avoid deletion upon app reinstallation however would this work across software resets? And surely there's a very small chance that two devices would randomly generate the same ID?
I think the best option might be to use UDID but I would like to know if, even though the UDID is incorrect as of ios7, is it still unique?
Yet another option is MAC address but as far as I know, there is no API for these
Please advise on the best option
Starting iOS 7 deducing MAC address isn't possible. You can, however, use below:
[[[UIDevice currentDevice] identifierForVendor] UUIDString]
Per Apple Documentation:
The value changes when the user deletes all of that vendor’s apps from
the device and subsequently reinstalls one or more of them. The value
can also when installing test builds using Xcode or when installing an
app on a device using ad-hoc distribution. Therefore, if your app
stores the value of this property anywhere, you should gracefully
handle situations where the identifier changes.
identifierForVendor is not supposed to change on reinstall of app:
The value in this property remains the same while the app (or another
app from the same vendor) is installed on the iOS device. The value
changes when the user deletes all of that vendor’s apps from the
device and subsequently reinstalls one or more of them. The value can
also change when installing test builds using Xcode or when installing
an app on a device using ad-hoc distribution. Therefore, if your app
stores the value of this property anywhere, you should gracefully
handle situations where the identifier changes.
https://developer.apple.com/reference/uikit/uidevice/1620059-identifierforvendor
However, I've just tested this with one of our live apps on the app store. Even with a number of other of our apps still installed on the device, if I reinstall app A the UUID returned from identifierForVendor changes every time.
It was not like this.
This used to work. But at some point, the UUID seems to have started changing on "simple reinstalls" (as stated above). Is this a known bug? Is identifierForVendor known to be broken versus the documentation above? Any workarounds (other than saving UUID to keychain, because that method breaks with iCloud syncing)?
It's a known bug. It seems like Apple made an update to AppStore that causes this new behavior for identifierForVendor around the 28:th May. If you search in the App Developer forum, there are other developers reporting the same problem.
The signature gc from Apple have replied on the issue with the following answer:
"Please file bug reports on this at https://developer.apple.com/bug-reporting>. We're aware of this issue and are investigating. There's no known workaround at this time."
identifierForVendor is expected to change when all vendor's apps are removed from the device. Also, it is bound to change if you're building and installing from Xcode directly.
The value in this property remains the same while the app (or another app from the same vendor) is installed on the iOS device. The value changes when the user deletes all of that vendor’s apps from the device and subsequently reinstalls one or more of them. The value can also change when installing test builds using Xcode or when installing an app on a device using ad-hoc distribution. Therefore, if your app stores the value of this property anywhere, you should gracefully handle situations where the identifier changes.
Source: UIKit/UIDevice/identifierForVendor
We are about to resubmit using an App Group entitlement to give us shared NSUserDefaults. It sounds like App Group NSUserDefaults (unlike keychain-access-group and iCloud key-value storage entitlements) are shared on the device, but not over the iCloud account. If the shared "deviceid" NSUserDefault key doesn't exist, we'll save the IdentifierForVendor ID and then use that for all our apps once it saved.
I'm experimenting a little with the identifierForVendor API.
As per the doc
The value in this property remains the same while the app (or another
app from the same vendor) is installed on the iOS device. The value
changes when the user deletes all of that vendor’s apps from the
device and subsequently reinstalls one or more of them. Therefore, if
your app stores the value of this property anywhere, you should
gracefully handle situations where the identifier changes.
In Debug or Release with Ad Hoc, I cannot replicate this behavior. The identifier still remains the same even if I remove all the applications I have installed for the same vendor (the reversed domain name I'm using, e.g. com.test).
Is this can be observed only for App Store distribution? Am I missing something?
I'm running on a iOS 8.3.
Related question: iOS7 - Device unique identifier.
I have one product that has two different applications. and both the applications it gives me different Identifiers for the same device (you would assume that apple would associate this to maybe your developer account so that you can reuse the information across your applications), but I was wondering is their anything that would give me the same identifier for a device on both the applications?
identifierForVendor is really what you want. UDID is a big NO on the AppStore. A user can opt out to advertisingIdentifier. Other ways (by MAC address, like ODIN1, and solutions that rely on UIPasteboard, as OpenUDID) will break on the future (hint: 7).
According to the docs, you should have the same identifier if both apps are from the same developer:
The value of this property is the same for apps that come from the same vendor running on the same device. A different value is returned for apps on the same device that come from different vendors, and for apps on different devices regardless of vendor.
The value of this property may be nil if the app is running in the background, before the user has unlocked the device the first time after the device has been restarted. If the value is nil, wait and get the value again later.
The value in this property remains the same while the app (or another app from the same vendor) is installed on the iOS device. The value changes when the user deletes all of that vendor’s apps from the device and subsequently reinstalls one or more of them. Therefore, if your app stores the value of this property anywhere, you should gracefully handle situations where the identifier changes.
OpenUDID is the best solution until now, even if it also may be changed if the device is reset.