Go to “udid.io” on your iPhone’s Safari application.
Step 2:
Click on the Tap to find the UDID option. After that, make sure you allow the website to download the configuration file when prompt.
Step 3:
Now go to Settings->General->Profile->Get Your UDID.
Step 4:
Tap on install located at the top right corner. Enter your iPhone passcode for confirmation.
Step 5:
Once it's installed, you will be automatically redirected to a Safari window that will display the UDID of your iPhone coupled with its product name and iOS build number.