What is UDID ?


How to

Every Apple customer will have come across the term UDID number at some time or other. You may even have been asked to provide it for something but how many of us actually know what the UDID is and what it is used for? Why is it such a big deal? The following will explain, what it is, what is used for and how it affects privacy.

What is a UDID?


The Unique Device Identifier is a 40-character combination of numbers and letters that is used to identify a particular iOS device. Each device has its own UDID, and you can find yours by going into iTunes with your device connected and click on Serial Number

What is the UDID Used for?

Because it is used to identify a device, the UDID number is used for connecting data to a specific device, i.e., an iOS Developer Account so that beta versions can be downloaded. It is also used by Apple to connect your device to your Apple ID so that you can download and install apps or music purchased through iTunes or the App store. It is used to upload your high scores to the iOS Game Center and for iMessages and notifications.


At one time, certain apps used to be able to access the UDID number of a specific device and transmit it, along with other identifying data, about a user, leaving that person and/or their device wide open to abuse. The data could be sold to other companies or “interested” parties and, as a result, when iOS 5 was released in 2011, Apple made it so that developers had to generate unique identifiers, accessible by a single app if needed and any app that tries to access a UDID number is rejected immediately from the iOS app store.

While it is unlikely that your UDID would be used for nefarious activities, you should take steps to protect your iOS device with a proper password, and two-step verification enabled on your Apple ID.

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