Unable to get UDID from iPhone Xs Max | iOS | Apple | iPhone

I need to get the UDID of my iPhone Xs Max to test my App. Apparently, That does not work on the iPhone Xs Max

You are getting an error because iOS 12 requires device management profiles to be installed over a valid HTTPS connection. That site's certificate is not trusted.

Better to use direct System Report or XCode to find UDIDs:

Answers: https://stackoverflow.com/a/52473809/342794 or https://stackoverflow.com/a/52997294/342794

Details on using udid.io (Specific to this question)

It seems you are using udid.io (http://get.udid.io -- No "https" !!??) to get UDID without any app installation or connecting to USB. security concern, this would fail with iOS 12.

Note: Even for older iOS devices, As it installs a certificate on the mobile device. Not really a recommended way. Could be a shortcut in case you don't have an alternative. Say if you have a large pool of QA devices and don't have physical access to the devices (device farms accessible over the network) and don't care about installing a certificate from the untrusted source. Even in that case, look for an alternative to use a script to find UDID for all connected devices (https://stackoverflow.com/a/52997294/342794).

On supported iOS:

a. Asks to install a certificate that gets deleted automatically.

b. Shows UDID on the browser with an option to email

Screenshots: