How to find UDID # iPhone 8

To get the UDID…

Connect to iTunes on older macOS or on Windows, or connect to Finder on newer macOS Mojave and later.

…In iTunes, select the device, and click the serial number shown in the general info. That should toggle the UDID.

…In Finder, select the device, and click on the model name in the upper left. That should toggle through several hunks of info, including UDID.

Xcode can also show this info, but that’s more than most folks want to wrangle.

I don’t know of a good way (a way that I’d trust) to get the UDID from on the device, and iPhone and iPad apps can’t get the UDID value. The UDID deliberately stopped being accessible to iPhone and iPad apps back around iOS 7.

I do see websites that suggest loading a profile downloaded from the website, an approach I would not use nor suggest. Profiles are very powerful controls.

I’m not aware of a good way to get the UDID value without the assistance of a Mac or Windows computer.

Related details for connecting to Finder or to iTunes:

Use the Finder to sync your iPhone, iPad, or iPod with your computer - Apple Support

Use iTunes to sync your iPhone, iPad, or iPod with your computer - Apple Support

If your computer doesn't recognize your iPhone, iPad, or iPod - Apple Support

I am not aware of a way to do that unless you are a developer.