What's a UDID? How do I find out my iPhone's UDID?

From time to time you'll need to find out the UDID for your iPhone (or your iPad). In this tutorial we show how to find out your iPhone or iPad's UDID, as well as what a UDID is and what you might need a UDID for.

(For the answers to similar tech jargon-related questions, try Macworld's glossary of tech terms.)

How to find out your iPhone's UDID: What is a UDID?

UDIDs are identifying numbers that are unique to individual iPhones and iPads (and iPod touch devices, for that matter). They're 40 characters long, and made up of a mixture of letters and numbers.

How to find out your iPhone's UDID: What do you use an UDID for?

The most likely situation you'll need your iPhone's UDID for is if an app developer has offered to let you try out some unreleased software. (As an app reviewer I'm occasionally asked for my Apple devices' UDIDs.) With a relevant UDID, a developer can register your device and give it access to non-official (non-App-Store-vetted) software. This is commonly used to let reviewers try out apps before they make it on to the App Store.

How to find out your iPhone's UDID: Is it dangerous to let someone know your UDID?

There's some debate about this, and you'll note in the screenshots below that I've hidden sections of my UDID to be on the safe side. But you should be okay.

What I would recommend is only to give your UDID to an app developer you trust, and to be cautious about the beta apps you agree to install (having your UDID won’t be enough for them to force software on to your device; you'll still need to accept the install). Be aware that when and if you accept (or beta-test) non-vetted app software there is some danger that it won’t work or cause unexpected effects - not necessarily as a result of malicious action, of course.

App developers are allowed a limited number of UDID registrations (these are effectively requests for permission from Apple to bypass the normal App Store download process) so it wouldn't make for a very efficient spam or malware dispersal mechanism; and the generally solid sandboxing between apps in iOS 7 and earlier makes it difficult to cause too much damage from a single app install - difficult, but not impossible.

(iOS 8 will see more intercommunication between apps, although even then we are assured that apps will have to seek permission from iOS itself to ask for information from other apps, making it sound like security will still be strong.)

How to find out your iPhone's UDID

Okay, this bit's really, really easy.

1. Plug your iPhone into your Mac, and go to iTunes (or start it up if it isn't already open).

2. Select the iPhone's icon at the top-right corner of the window, underneath the search box. (If you've got more than one iOS device plugged in, this button will say '2 devices' instead - press it and then select the iPhone.)

How to find your iPhone's UDID

3. You'll now see the iPhone's summary page. (If it's showing apps, podcasts or whatever, select Summary from the top bar of tabs.) You can see the iPhone's capacity, phone number and serial number in the top box; click on the serial number and this will change into the UDID.

How to find your iPhone's UDID

How to find your iPhone's UDID

4. After the serial number changes into the UDID, pressing Apple + C at the same time will copy the UDID to the pasteboard. Alternatively, right-click it and select Copy.

How to find your iPhone's UDID

5. Find a blank document and paste the UDID into it by pressing Apple + V.

That's it - easy.

How to find out your iPad's UDID

For an iPad the process is almost exactly the same - just pick the iPad option from the dropdown menu if you’ve got more than one device plugged in.

1. Plug your iPad into your Mac, and go to iTunes (or start it up if it isn't already open).

2. Select the iPad's icon at the top-right corner of the window, underneath the search box. (If you've got more than one iOS device plugged in, this button will say '2 devices' instead - press it and then select the iPad.)

3. You'll now see the iPad's summary page. You can see the iPad's capacity and serial number (but not phone number, of course) in the top box; click on the serial number and this will change into the UDID. (Clicking again may produce further identifying numbers - see below)

4. After the serial number changes into the UDID, pressing Apple + C at the same time will copy the UDID to the pasteboard. Alternatively, right-click it and select Copy.

5. Find a blank document and paste the UDID into it by pressing Apple + V.

The top box of the iPad's Summary tab doesn’t have a phone number, of course. It just shows the capacity and the serial number. Click the serial number, as before, to change it into the UDID, and press Apple + C or right-click and select Copy.

One difference you may find with cellular-equipped iPads (rather than WiFi-only models) is that when you click the UDID it won't go back to the serial number right away; it'll cycle through various other identifying numbers: Mobile Data Number (unknown, in my case), MEID, IMEI and ICCID. Finally it goes back to serial number.