Differences Between Udid and Uuid

Differences between UDID and UUID

UUID (Universally Unique IDentifier) Is on a per-app basis. identifies an app on a device. As long as the user doesn’t completely delete the app, then this identifier will persist between app launches, and at least let you identify the same user using a particular app on a device. Unfortunately, if the user completely deletes and then reinstalls the app then the ID will change.

UDID (Unique Device Identifier)
A sequence of 40 hexadecimal characters that uniquely identify an ios device. This value can be retrieved through iTunes, or found using UIDevice -uniqueIdentifier. Derived from hardware details like MAC address.

Whats the difference between UID and UDID?

This explains it well: Differences between UDID and UUID

UUID (Universally Unique IDentifier), what you call UI - An id that's per app. It's also per install so if a user reinstalls the app it will be different.

UDID (Unique Device Identifier) - Is unique to your phone, it's used by apple mainly and is universal between apps.

How to identify iOS device uniquely instead of using UUID and UDID

Apple has done away with the approach of UDIDs and will reject apps that use the same for unique device identification.
Source: TNW

What you are looking for is Vendor ID

How unique are the ids generated with CFUUID , in iOS?

When you say that apple doesn't allow the use of UUID, you must be referring to the UDID, or Unique Device ID.

A UUID is unique every time you generate one. It's not simply a UDID. UUIDs are unique globally.

Is it unique for every device? If yes how is it different from UDID?

Yes, it's unique for every device because part of a UUID is a devide ID, though it's not the entire UDID. The UDID is always the same. Each time you create a UUID, it's different from the last, so you would need to store the UUID if you wanted to use it as a device ID.

Is it a random generator? If yes how good is it? Can i be sure that in
10000 devices there wont be a duplicate?

A UUID is computed, not randomly generated. The first part is a form of device ID, and the second part is derived from the date and time. While the date and time part of a UUID may be duplicated between devices, the device ID portion still guarantees unique UUIDs globally.

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