Archive for August, 2011

RIP: Apple’s unique and persistent identifier (UDID)

Monday, August 22nd, 2011

It is now official: Apple will retire the unique identifier (UDID) that was used by many mobile ad networks to track application downloads, and measure ad effectiveness. The UDID was used instead of a mobile cookie, by uniquely and persistently identifying the user’s mobile phone. Uniquely, because every phone had a different number; persistently, because even after a power cycle, the number remained the same.

This sounds very much like a traditional web cookie, but there are two main differences. A web cookie is associated with the consumer’s browser, and can be deleted by the user. The UDID is a hardware identifier, which cannot be deleted.

What was the UDID used for?

Advertisers used the UDID to attribute downloads to specific ads. The UDID allowed them to make the connection between where (to which devices) an ad was shown, and if that device ended up making a download.

Why did Apple remove it?

Despite the fact that no personal data was exchanged, Apple and a few high profile publishers were recently sued by some gold diggers. These suits alleged that the inability to turn UDIDs off violated consumer’s privacy. Apple could have adjusted the operating system by giving consumers the ability to toggle the UDID on/off (much like iOS handles location), but instead Apple simply turned it off.

What impact will it have?

It will have a negative impact on the amount of CPA (Cost per Action/download) advertising dollars flowing into the ecosystem. Most CPA campaigns rely on the ability to track campaign effectiveness. The growth in this area will be hindered.

Are there alternatives?

The alternative to a hardware identifier is a browser cookie. Apple iOS devices -such as the iPad and iPhone- use the safari browser, which has “third party cookies” turned off by default. This means that publishers can write first party cookies, but advertisers are not able to use the cookie to measure ad effectives.

So now what?

The good news is that “brand budgets” and “location-based campaigns” will not be affected. Targeting consumers while they are utilizing certain applications (e.g. sports applications) or in certain locations (e.g. Boston) is still possible. Performance campaigns that optimize on click through rates are also unaffected. As a result, much of today’s mobile advertising will remain intact.

In conclusion, the deletion of the UDID is a move that will certainly have an impact on a subset of the mobile advertising ecosystem – especially CPA campaigns targeted to iOS. Multiple forms of mobile advertising will remain unaffected, and perhaps iOS dollars will flow into other operating systems and handsets.