I’m gonna preface this piece by saying that there are a lot of unknowns. I’m almost certainly wrong on parts, but mostly, we just don’t know so many things. At an unknown time, but in the next few months (quite possibly weeks), Apple is rolling out a major update to iOS. After this, when you open up many apps for the first time, including Facebook, you’ll get a message something like: Allow “Facebook” to track your activity across other companies’ apps and websites? [Ask App not to track][Allow] I’m gonna go out on a limb and say most people are going to say ‘no way!’ If you select ‘no’, those apps lose a very big chunk of the data they currently collect. What percentage of people say no is a big unknown. Perhaps people have been trained by all the “accept cookies” messages and just click ‘allow’? No-one is sure.  This affects all apps – Pinterest, Linkedin, etc – but as far as apps and advertising goes, and especially for online retailers, Facebook is the big one. There’ll likely be an impact on Google as well, but a relatively small one. Retailers with their own apps will be affected as well, but that’s another discussion.  While it’s true that there are a lot more Android phones than iPhones in the world, as far as online retail goes, for most companies, it’s an iOS game. I’ve reviewed a few Facebook ads accounts and roughly 70 – 75 per cent of all impressions are served to iOS devices. So the potential impact is significant. Facebook has indicated it will treat all devices the same – so you won’t get rich Android data and then limited iOS data. What this looks like in reality, no one knows – I don’t think Facebook are 100 per cent clear themselves.  We’ll lose three things: 1. Targeting options  We won’t be able to have all the options we have now. I’m not 100 per cent sure which options will be lost, but some will be, especially detailed retargeting.  2. Advertising efficacy  Facebook’s advice over the last few years has been increasingly “let the algorithm do its thing”. The problem is now that the algorithm has far less data about what happens outside Facebook, it will optimise your ads less effectively.  3. Accurate reporting  Facebook’s mantra about the data flow from iOS devices is “restricted, aggregated, and delayed”. Our reporting simply won’t have the level of depth, accuracy, and timeliness that we have become used to.  Attribution will also be changing. It will now be seven days post click, with limited view data. For those uploaded on 28/1 or 7/1, we should expect to see the reported performance drop. It’s important to note that reporting doesn’t change reality. Just because you change the reporting from 28 days to seven days doesn’t mean people just suddenly stop buying on day eight. But our ability to understand this via reporting will be limited. I believe even these seven days have limitations in some cases but we’re getting deep into uncertain territory here.  A good way to think about what data is lost is: does this data come from within Facebook itself, or from your site and other sites visited? If it’s within Facebook, all good. For example, lead generation ads will have little direct impact as they all happen in Facebook – although Facebook’s ability to understand who should see those ads may be impacted as that’s supplemented with site visitation data. If it’s from other sites, e.g. which products are viewed on your site, there will be some impact.  There’s a number of other changes I’m not getting into here, such as restricted events – this will have no impact on most companies, but a massive impact on a few, especially more sophisticated global companies).  I would love to add a happy ending that says “do these three things and everything will be ok”. But unfortunately I can’t. The true impact just won’t be known for at least a few months, maybe more. If you are dependent on Facebook, expect significant change.