iOS7 Day-by-Day :: Day 9 :: Device Identification

Written by Sam Davies

This post is part of a daily series of posts introducing the most exciting new parts of iOS7 for developers –#iOS7DayByDay. To see the posts you’ve missed check out the introduction page, but have a read through the rest of this post first!


Today’s post will be quite brief, but is an important one for any developers who have have been using the device unique ID to track their users. There are many reasons that you might want to use the device ID, however it can also be deemed a privacy concern – allowing tracking of users without their permission.

The code for this blog post is available in the github repo which accompanies this series – at

The device UDID was deprecated in iOS5, and has been removed in iOS7. iOS6 introduced alternatives, which are now the only approaches which are supported:

Vendor Identification

The closest replacement for uniqueIdentifier is another method on UIDevice – identifierForVendor, which returns aNSUUID. This is shared between all apps from the same vendor on the same device. Different vendors on the same device will return different identifierForVendor values, as will the same vendor across different devices.

This value provides pretty much the same functionality from the point of view of the app developer, but without the privacy concerns for the user.

It is worth noting that if a user uninstalls all apps for a specified vendor then the vendor ID will be destroyed. When they install another app from that vendor a new vendor ID will be generated.

Advertising Identification

If you need a unique ID for the purposes of implementing in-app advertising (irrespective of whether it is iAd or not) then an alternative approach is required. The AdSupport module includes a class called ASIdentifierManager which has aadvertisingIdentifier method. This returns a NSUUID which may be used for the purposes of tracking advertising. There is also a method advertisingTrackingEnabled, which returns a BOOL specifying whether or not a user has allowed advertising tracking. If the return value is NO then there is a short list of things that the app is allowed to use the ID for – none of which involves tracking users.

The advertising ID is unique across an entire device – so that if tracking is enabled ads can be tailored to the specific user. More often than not an app developer won’t have to interact with this class, but will instead drop in an ad-serving framework which will use the ASIdentifierManager class behind the scenes.

Network Identification

When uniqueIdentifier was deprecated, using the device’s MAC address became popular. A MAC address is a unique identifier allocated to every piece of networking equipment in the world – from WiFi adaptors to datacenter switches. It’s possible to query an iOS device for its MAC address, which will be both unique and persistent – so ideal for tracking. However, with iOS7, Apple have made it impossible to obtain the MAC address programmatically on an iOS device – in fact a constant will be returned:02:00:00:00:00:00. This closes this ‘loophole’ and will drive developers to the Apple-preferred device identification approaches.



Apple are stamping out the alternatives to device identification, so now’s the time to adopt their chosen approach. This offers greater privacy for the end user, so it’s a good thing to do.

The attached sample project with this post (WhoAmI) gives a brief demo of the different approaches we’ve outlined here.

Don’t forget that you can get the code for this project on github at If you have any feedback/comments then feel free to use the comments box below, or hit me up on twitter – @iwantmyrealname.