The UDID is an identification number (Unique Device Identifier) that they equipped Apple devices with. As the name suggests, the UDID is unique; it means it cannot be changed and thus remains constant over the entire service life of the end device.
If you have commissioned an app development, the developers can explicitly release an app for your UDID by creating a “provisioning profile.” After storing this profile, you can install the app directly on your device without downloading it from the App Store. This allows you to assess the status of the app before it is finished.
Identification via the UDID works similarly to IP addresses on the Internet, but an IP address can be hidden or changed. The UDID on the other hand is firmly linked to the respective device.
The identification via UDID is also comparable with that of a PC via the cookies stored there. As a user, you cannot block access to the UDID, as is possible with cookies or regarding websites. But you can delete cookies, but not a UDID.
Data protection on a PC has been far better than protecting your data on an iPhone or iPad. After analyzing your data, the app providers know you better than you do themselves and use this for advertising.
Since apps have so far been able to read all of your contacts easily, the profile data can be linked to the names, addresses, telephone numbers, and social media accounts of the data victims and then sold at high prices.
This violates data protection laws in Germany and Europe, and there are also violent protests against UDID access in the USA. Still, as long as Apple allows this, and the legislature does nothing, you will continue to be spied on.
The UDID is a unique alphanumeric combination attached to your iOS device. Every iPhone, iPad, and iPod touch has one. It’s pretty easy to find yours. What makes it so important is that the UDID of your device is only customized to you and cannot be hacked or tweaked by a third party. So, even when your device is stolen or missing, with the UDID, you can quickly locate where it is.
Also, this means that if the application is uninstalled or you reset your device, it will remove immediately the installation ID so that no other person can access your account. Also, the identifier is encrypted on the device and hence not available to other developers.
You might want to try out how easy it is for apps to access your UDID. It can also be helpful that you know the UDID of your iPhone, for example, if you want to take part in a beta test.
Apple does not display the UDID on the iPhone via settings, but iTunes shows it when you connect the iPhone or iPad to the PC. Select the device in iTunes and click Overview, then Serial Number. The UDID will then be displayed.
In closing, it is now clear that the UDID is vital for the safety of your devices if lost or stolen. Hence, it is beneficial for the user to be aware of the UDID and its significance when the need arises.