As you make your morning rounds on social media, you notice a new ad on your Facebook feed. It’s for that clothing store you were clicking around on last night.
And it’s offering you free shipping on that t-shirt you were eyeing!
Excitement quickly fades to confusion. You don’t even have an account with the store, let alone one that’s linked to your social media.
So how did your online window shopping end up connected to your Facebook profile?
The day goes on and the strangely-personal ad fades from your mind.
On your lunch break, you respond to a few obnoxious political Tweets and post a couple of your own thoughts on the government. Your candidate is the only reasonable choice, and you want to make sure everyone knows it.
As quitting time approaches, you scroll through your favorite recipe blog on your phone, trying to decide what’s for dinner.
But in between the mouth-watering photos and vaguely-relevant stories, you see your presidential pick beaming from a banner ad.
You feel that weird jolt of confusion once again. Your apps, seemingly discrete at first glance, seem to be communicating with one another.
And they appear to be doing so in order to show you more ads.
Don’t worry – these perceptions don’t mean you’re crazy. In fact, you’ve just discovered one of the biggest open secrets in the tech industry.
All of your apps on all of your devices collaborate to serve you activity-based ads. And they do so by collecting your device’s advertising ID.
By linking your activity to your unique advertising ID, apps provide ad companies with complete profiles of your preferences, habits, likes, dislikes and more.
This profit-driven practice has profound implications for your privacy, but there are ways to regain control over it.
We’ve got everything you need to know about advertising IDs – let’s get started.
What Are Advertising IDs?
Your phone has many different unique identifiers associated with it. Each has a different purpose, but they all have something in common: they specifically identify your device.
Your serial number, for instance, is the permanent ID number associated with your phone. And your SIM serial number is the unique ID attached to your SIM card.
There’s also your MAC address, the special ID used to identify your device on networks. Not to mention your phone number, email account and all the usual identifiers.
But there’s one very valuable identifier that most users aren’t even aware of: your advertising ID.
Most apps collect some amount of information about your device, such as your OS version and phone model. Apps that display ads will also collect your advertising ID, which they send to ad providers along with other data about your in-app activity.
Your in-app activity encompasses everything you do in an app. The posts you like, the comments you make, the profiles you view, the games you beat … it’s all valuable data. And it’s all packaged together with your advertising ID.
Since your advertising ID is unique to your device, the ad provider can then use it to link this new data with your data from other apps.
The result is a profile of you that’s then analyzed in order to determine which ads you’re most likely to click on.
Every ad click represents more earnings, so companies will go to great lengths to maximize clicks. And since you’re more likely to click on an ad that matches your interests, having a profile of those interests is invaluable.
Next time you load a site or app, the ad server will match your device’s advertising ID with your ad profile. It will then show you ads based on the data amassed from all your prior activity.
All the while, it’ll continue collecting new data via your apps and your advertising ID.
Think of your advertising ID like a Social Security number for ads. All of your financial history is linked to your SSN, so new creditors can use it to view your financial profile. And all of your app activity is linked to your advertising ID, which advertisers use to serve you more relevant ads.
Is Advertising Really That Lucrative?
In a nutshell, yes – and even more than you think.
We categorize Google, Apple, Microsoft, Facebook and their ilk as tech companies in our heads. But it’s probably more accurate to think of them as ad companies instead.
Here’s an example of why: in 2018, Google made 116.3 billion dollars in ad revenue.
These astronomical profits were no doubt enabled, at least in part, by the 2.5 billions active Android devices around the world. Each of those devices has its own advertising ID.
That means billions of advertising profiles actively generating ad revenue.
Advertising profits would be much smaller were it not for personalized ads. So advertisers are constantly working on new ways to make ads even more personal, relevant and clickable.
And advertising IDs make it all the easier.
Why Is There a Separate Advertising ID?
With so many other unique identifiers available, why does there need to be one specifically for ads?
Until 2013, that wasn’t the case. Apps would simply send device serial numbers and other persistent identifiers to ad providers.
The end result was mostly the same: a unique ID was used to link all your activity together. But there were some problems with this system.
For instance, if you sold your phone, the device user would change, but the serial number would remain the same. The new owner’s data would thus be combined with your old data in the ad provider’s profile.
Additionally, privacy-conscious users were concerned about the lack of control they had in this process. A serial number or IMEI can’t be reset or changed, so there was no way for users to control their data.
So in 2013, both Apple and Google implemented the advertising ID to remedy these problems.
The advertising ID could be reset at will and was usable exclusively for advertising purposes. This eliminated further privacy concerns regarding the distribution of sensitive serial numbers.
Inevitably, new problems arose from this new feature. Apps could still theoretically transmit other identifiers along with advertising IDs, making the reset function useless.
An advertiser could receive two sets of data with the same serial number, but different advertising IDs due to a user reset. Because of the serial number, the two data sets could still be linked to the same profile.
The user would have the illusion of control, but resetting the advertising ID would be effectively pointless.
Google and Apple attempted to combat this by prohibiting apps from transmitting other identifiers alongside advertising IDs.
Additionally, both companies prohibit the use of any persistent identifier other than the advertising ID for advertising purposes.
The Android Advertising ID policy requires explicit user consent before the advertising ID can be transmitted with other IDs.
What’s the Difference Between Advertising IDs and Cookies?
Web ad trackers are nothing new – they’ve been around almost as long as web ads themselves. And most people are aware of their most common form: cookies.
These tiny files reside in your web browser and let advertisers track your pageviews, clicks and other activity.
But as widespread as they are, cookies are only so useful to advertisers.
For starters, more and more users are getting wise to cookies and blocking them with browser extensions. One analysis found that 64% of tracking cookies were blocked by web browsers.
Even unblocked cookies are still susceptible to user interference. It takes just a couple of clicks to delete cookies, and they can be erased individually or en masse.
Cookies are also site-specific, so websites and ad providers must match their cookies to serve personalized ads.
It’s a tricky and resource-intensive process: 40% or more of all cookie matches are incorrect or unsuccessful.
That means that 40% or more of all cookie-based personalized ads aren’t actually relevant or accurate.
Advertisers are increasingly moving away from cookies and towards persistent advertising IDs.
Unlike cookies, an advertising ID remains the same across all apps and sites. No synchronization is needed for different companies to track the same advertising ID.
Although advertising IDs can be reset or disabled by users, they’re not as widely known as cookies. Users are much less likely to regularly reset their advertising IDs than they are to wipe cookies regularly.
The consistency and unity of advertising IDs holds a lot of appeal for ad providers.
How Do Advertising IDs Violate Your Privacy?
When your personal data becomes a commodity, your privacy is inherently at risk.
Companies that profit from user data will, of course, prioritize that data over the users themselves. And that data is in high demand by many bad actors, from rogue developers to malicious advertisers.
The privacy problems begin with the apps that collect your advertising ID.
Officially, apps are only allowed to send advertising IDs to advertisers; no other IDs can be transmitted. In practice, though, this privacy-protecting rule is often simply ignored.
A survey performed by privacy analysis company AppCensus revealed some shocking offenses pertaining to advertising IDs.
Of the 24,000 surveyed Android apps that collect advertising IDs, around 17,000 also transmit other identifiers to advertisers.
That’s around 70% of apps in violation of Google’s policies – and of your trust.
These aren’t just small-time apps, either. Many offending apps have hundreds of millions of downloads; some are even household names.
The list includes apps like Clean Master, Flipboard, Temple Run 2, Cooking Fever and Audible.
Excessive Data Collection
There’s also the matter of what, exactly, advertisers are getting alongside your advertising ID.
Such data could be as simple as the types of mobile games you like or the news articles you read. But it could also get much more personal.
An innocuous to-do list app could be distributing that list to advertisers.
Suddenly, “buy wine” and “make gyno appointment” could turn into ads for rehab centers and birth control. Combined with other information in your ad profile, like email or home addresses, this data could do even more damage.
Location and purchase data are huge moneymaker as well.
Companies can find out which stores you visited, how long you were there and how much you spent. You probably didn’t think that your weather app would track you like this when you installed it!
The real danger lies in the fact that all of this data has one thing in common: your advertising ID.
It’s not just one or two pieces of data that relate to you. Rather, it’s everything you do compiled under your unique advertising ID.
Advertising IDs may not stick with you the way your name, address or SSN do. But the sheer volume of data associated with them is often enough to deduce those data points anyway.
In fact, thanks to advertising IDs, advertisers may very well know you better than anyone else.
What Are the Different Advertising IDs and How Do You Find Them?
Whether you use an Android phone, an iPhone, Windows or Mac, you’ve got an advertising ID.
In fact, just about every OS has its own advertising ID, though it goes by different names on each platform.
Here’s the skinny on each one, as well as how to find and reset them.
Android Advertising ID/Google Advertising ID
Whether it goes by Android Advertising ID (AAID) or Google Advertising ID (GAID), if you use Android, you’ve got this.
Google assigns these randomly-generated unique IDs to every Android device. Thankfully, it’s pretty easy to find and reset this ID, as well as limit its use in the future.
How to View and Reset Android Advertising ID
Simply navigate to Settings > Google > Ads to get started.
At the bottom of the screen, you’ll see your unique advertising ID. It’ll look like a long jumble of letters and numbers; copy it down somewhere for safekeeping.
Once you’ve got the ID recorded, you can go ahead and tap on “Reset advertising ID.”
A confirmation pop-up will appear. Hit “OK” and you’ve now got a fresh, unused advertising ID.
If all you wanted to do was reset your ID, you’re all set. But if you want to stop your advertising ID from being collected in the future, there’s one more step.
How to Opt-Out of Android Advertising ID
Under the “Reset” option, toggle “Opt out of Ads Personalization” on.
This will inform apps that you don’t want your advertising ID collected. However, it’s not strictly enforced and apps may still collect it anyway.
Though some apps don’t abide by the honor system, many do. These apps will cease collecting and distributing your advertising ID.
You’ll still see ads, but they’ll be random and won’t be based off a secretly-assembled data profile.
Apple ID for Advertising
Apple’s ecosystem is generally more closed-off than Android’s, and its ID for Advertising (IDFA) is no exception.
Though the ID itself is more hidden, resetting it is just as easy on iOS and macOS as it is on Android.
How to View and Reset Apple ID for Advertising on iOS
The IDFA is not made available to the user like Android’s is. If you want to view it on iOS, you’ll need to get a third-party app.
Open one of these apps and you’ll see various device stats, including your IDFA. It’ll look like a long string of letters and numbers; write it down somewhere for safekeeping before continuing.
To reset your IDFA, head to Settings > Privacy > Advertising, then tap “Reset Advertising Identifier.”
A confirmation prompt will appear. When it does, tap “Reset Identifier” and voila – you’re in the clear.
How to Opt-Out of Apple ID for Advertising on iOS
If you want apps to stop taking your IDFA altogether, toggle “Limit Ad Tracking” before you close the Settings.
Unlike Android’s equivalent, this option actually prevents apps from collecting your IDFA. It works by replacing all characters in your IDFA with zeroes, making the number unusable even if it’s collected.
How to Reset and Opt Out of Apple ID for Advertising on macOS
The IDFA resetting and disabling process on macOS is very similar to the process on iOS.
Go to System Preferences > Security & Privacy > Privacy, > Advertising.
From there, you can click “Reset Advertising Identifier” to reset your IDFA or toggle “Limit Ad Tracking” to disable it.
Windows Advertising ID
Windows 10 is everywhere – laptops, desktops, tablets and phones.
The consistent user experience across all devices is a big draw for this OS. But another consistent aspect is considerably less appealing: the Windows Advertising ID.
How to View Windows Advertising ID
Unfortunately, there’s no easy way for users to view their own Windows Advertising IDs.
If you want to see yours, you’ll need to find it in the registry. Take care not to accidentally modify any registry keys during this process – doing so could break various OS functions.
To open the registry, press Windows+R and type “regedit” (without quotation marks).
Once it’s opened, navigate to ComputerHKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionAdvertisingInfo.
You can copy and paste the location (minus the ending period) into the bar at the top or use the left panel to navigate.
In the right panel, look for the entry with the name “id” and you’ll find your ID next to it in the “Data” column.
If you don’t see an entry named “id” then you’re in luck – your advertising ID is already disabled.
However, if you do see an ID, write it down for safekeeping, then close the registry.
How to Reset and Opt Out of Windows Advertising ID
To reset or disable the Windows Advertising ID, open the Settings app.
Go to Privacy > General and toggle “Let apps use advertising ID to make ads more interesting to you based on your app activity” off. Doing so will reset your advertising ID.
If you turn it back on, you’ll be assigned a brand new ID. But we recommend leaving it off, as that will prevent any Windows apps from collecting and redistributing it.
Why Do You Need to Record Your Advertising IDs?
Throughout this guide, we’ve advised you to record any and all advertising IDs before resetting them.
Why? It’s simple: you need it if you want to scrub your data from ad providers.
Whether or not you do this depends on your individual privacy preferences.
Some folks are content with simply not receiving personalized ads anymore. Others would rather have all previously-gathered data erased from advertising databases.
If you fall into the latter camp, you’ll need your advertising ID(s) in order to make removal requests.
Be aware that not all advertising companies allow you to request removal of preexisting data. With many of them, your only recourse is to opt-out of future profiling by resetting and disabling your advertising ID.
Summary: Your unique advertising ID is collected alongside your browsing activity and sold to advertisers. They use it to show you personalized ads – and make huge profits in the process.