Find iPhone UDID without iTunes...or a working iPhone

Like a lot of us last Monday, I really wanted to get the iOS 7 beta on my iPhone, but didn’t currently have an iOS Developer Program membership ($99/year). (The last time I felt compelled to get a developer beta was for iOS 5, mainly because I wanted/needed Notification Center.)

I got home from work really late Monday night and couldn’t wait to get the beta installed, and in my haste I made a mistake that, at the time, I thought might have bricked my iPhone. (Keep in mind too that you’re warned you can’t revert to an earlier version of iOS (i.e., non-beta) if you install the beta, which, it turns out, isn’t true.)

I installed the beta (~1:30AM), booted up the phone, and iTunes wouldn’t recognize it, because I hadn’t associated my UDID number with my reactivated dev account. Not only had I not taken this step before installing the beta, I hadn’t even written down my UDID at all. (I should have been able to search my email for this, as I’d previously sent it to various devs for beta access to their apps, but, long story short, I get new iPhones fairly often because I’m a maniac, and just hadn’t grabbed the UDID for this latest one yet.)

The UDID is a 40-character string that uniquely identifies the phone–the hardware–and is easily accessible if you have a working iPhone. One way is via iTunes: when the phone’s plugged in, choose the “Summary” tab in iTunes and click on “Serial Number”, and you’ll see it change to “Identifier (UDID)”, followed by the UDID. (⌘C will copy the string to your clipboard.)

Another way is through OS X’s System Information app: click the apple icon in your menubar → About This Mac → More Info… → System Report… Once you have the System Information app open, look for USB under “Hardware”, and then look for your phone in the USB device tree, and note that the UDID is actually reported as the “Serial Number” here. (I’m pretty sure this method won’t work (at least on OS X) if iTunes doesn’t recognize your phone.)

Another method you can use if you have a working iPhone is to download apps whose sole purpose is to report this string. Search the App Store and you’ll find plenty of them.

OK, that’s all well and good, but what do you do if iTunes isnt’ recognizing your device, and your device won’t boot fully? As I was scrambling around trying to find a solution that would salvage my phone, it occurred to me that I had seen folders made up of long sequences of characters in a backup folder I had been poking around in some time ago. I went snooping and again came across those long sequences in this folder (where iTunes stores your iOS backups):

~/Library/Application Support/MobileSync/Backup/

I counted up the characters, and sure enough there were 40 for each folder at the above location. I rummaged through the various .plist files to figure out which of these folders/sequences corresponded to my iPhone 5 (and not my iPad, other iPhones, etc.), punched that string into my dev account, and all was right with the world.

(Clearly this isn’t rocket science, but I decided to write something up for other non-devs who may come across this issue in the future and go so searching for a solution.)