If you've updated to the latest version of Apple's iOS, 14.5, and still haven't seen any privacy pop-ups, it could be because of a setting on your iPhone

• "App Tracking Transparency" is a core new feature of Apple's iOS 14.5 software update.
• App developers now need to serve users a pop-up asking for permission to track them.
• Some users' settings have prevented them from seeing any pop-ups. Here's how to change that.

Apple's iOS 14.5 update, which began rolling out earlier this week, has a bunch of new features, from emoji to new voices for Siri.

Arguably the most significant update is the introduction of "App Tracking Transparency," which requires app developers to serve pop-ups explicitly asking people to opt in to being tracked across other companies' apps and websites.

However, some people who've updated to iOS 14.5 haven't seen any permission pop-ups.

Mobile-advertising experts suggested three possible reasons. Apple did not respond to requests for comment.

1. The 'allow apps to request to track' privacy setting is toggled off

The simplest explanation for not yet seeing the pop-ups boils down to an option in a user's privacy settings.

To check if that's the case, head to the Settings app and scroll down to "privacy." Clicking on "tracking" shows a screen that looks like the image below, with the option to toggle "allow apps to request to track" on or off.

If the toggle is off, apps will be prevented from sharing that device's Identifier for Advertisers, or IDFA, with other apps and companies (unless the person has previously given permission for certain apps to track them).

Simon Poulton, the vice president of digital intelligence at the digital marketing agency Wpromote, said it was most likely that people with this setting switched off had "limit ad tracking" switched on in previous versions of iOS. In his view, the two settings aren't the same thing but are being treated as such by Apple.

The previous setting "was about ad tracking, obscuring the IDFA to mitigate ad tracking, but App Tracking Transparency is far broader, and there are lots of factors here - I don't think you can make the case that opting out of that is the same thing," Poulton said.

"It's another screw turning" for players in the mobile-advertising market, he said.

2. Some users might not have the option to toggle 'allow apps to request to track' on

Some people have reported that the "allow apps to request to track" option is grayed out, rendering them unable to opt in to receiving the notifications.

Apple says on its support page that this will affect users under 18 or devices with child accounts; Apple IDs managed by an educational institution or other organization that limits tracking; and Apple IDs created within the past three days.

However, Insider found at least two instances of users who didn't fall into these categories but were unable to toggle the setting. The mobile-measurement firm AppsFlyer said in a blog post last year that some people had been able to reset the toggle by logging out of their iCloud accounts and logging back in again.

3. Some apps haven't rolled out the prompt yet

While many developers began serving the privacy pop-up immediately after the iOS 14.5 update rolled out on Monday, others are waiting a little longer.

"Some brands have decided they will not show the ATT prompt on the first open," Poulton said. "You just get one shot" to show the user the pop-up, he added, and some developers are waiting to see how things shake out before proceeding. That does mean, however, that those apps will not be able to access user IDFAs in the interim.

"After I installed iOS 14.5, I was surprised how few applications presented me with a pop-up," said Aaron McKee, the chief technology officer of Blis, a location-focused adtech company that helps advertisers target consumers. "I didn't see one in Twitter, Facebook, Reddit, Snap, LinkedIn, Uber, Uber Eats, Deliveroo, TripAdvisor, or almost any other game or utility app I could find on my phone."

McKee said that on Thursday, 30% of iOS 14.5 bid requests across Blis' network arrived with an IDFA present, meaning those users had opted in to tracking. But for the previous version of iOS, 89% had an IDFA attached.

"Some users understand the value exchange that exists between apps and publishers - sharing a bit of (mostly pseudo-anonymous) data means that apps can continue to provide free content," McKee said. "It also appears that a significant cross-section don't want to be part of that value exchange, and advertising and adtech companies should ensure they have a future-proofed, privacy-first approach to reaching their audiences."

Bonus: Users can check whether they're opted in to receiving 'personalized ads' on Apple's services

At the bottom of iOS 14.5's privacy settings is an "Apple Advertising" page where people can choose whether Apple can serve "personalized ads" to them in the App Store, Apple News, and the Stocks app. Apple is preparing to launch an ad format in the App Store that suggests apps a person might like to download.

Apple has said that it does not track users and that its own apps don't share information for advertising purposes with other apps and companies. However, the fact that Apple's setting works on an opt-out basis and appears in a separate menu has been a bone of contention among members of the mobile-advertising community.

"It's certainly something the mobile-ad industry isn't impressed with," said Shumel Lais, CEO of the analytics platform Appsumer. "But ultimately Apple can get away with it, as it can serve personalized ads using its own attribution solution without having to expose user identifiers to advertisers."