Given a choice, would any of us want to be followed online to see more relevant digital ads?

We’ll find out in a moment.

On Monday, Apple released iOS 14.5, one of the most anticipated software updates for iPhones and iPads in years. It includes a new privacy tool, App Tracking Transparency, which gives us more control over how our data is shared.

Here’s how it works: when an app wants to track our activities in order to share information with third parties such as advertisers, a window will appear on our Apple device asking for our permission. If we say no, the app will have to stop monitoring and sharing our data.

A pop-up window might sound like a little design tweak, but it has caused an uproar in the online advertising industry. Above all, Facebook has gone on the warpath. Last year the social network launched a website and ran full-page ads in newspapers denouncing Apple’s privacy policy as harmful to small businesses.

A big motivator, of course, was that the privacy settings could affect Facebook’s own business. If we’re not being followed by Facebook, it’s harder for the company to see what we’re shopping for or what we’re doing in other apps, making it harder for brands to target us with ads. (Mark Zuckerberg, CEO of Facebook, has denied that his company’s business is being affected by Apple’s policies.)

“This is a big step in the right direction, if only because it makes Facebook work up a sweat,” said Gennie Gebhart, director of the Electronic Frontier Foundation, a digital rights nonprofit.

But she added, “A big question is, will it work?”

Ms. Gebhart and other privacy professionals said Apple’s new feature may not be enough to end dodgy tracking on iPhones. It could just make developers and ad tech firms find loopholes so they can keep tracking people in different ways, she and others said.

I’ve been testing early versions of iOS 14.5 for about two months to get used to the new privacy controls and other new features. Few developers have tested the pop-up with the public, so my understanding of how well the privacy feature works has been limited.

However, I’ve found that iOS 14.5 has other important new features as well. One of them is the ability to use Siri by default to work with a music player other than Apple Music like Spotify. This is a big deal: in the past, voice assistant was not convenient to use with other music services.

Here’s what you need to know about Apple’s new software:

It’s important to understand how tracking works in apps.

For example, let’s say you’re using a shopping app looking for a blender. You look at a Brand X mixer and close the app. Later on, ads for this mixer will be shown on other mobile apps like Facebook and Instagram.

Here’s what happened: The shopping app hired an ad tech company to embed trackers into the app. These trackers checked information on your device to identify you. If you’ve opened other apps that work with the same ad tech company, those apps were able to identify you and serve you ads for Brand X’s mixer.

Let us help you protect your digital life

With Apple’s new data protection feature, you can decide if this should happen. Now when you open some apps, a pop-up window will appear: “Allow [App Name] to track your activity across other companies’ apps and websites? “You can choose between ‘Don’t track the app’ or ‘Allow’.

If we select “Don’t Track App”, two things happen. The first is that Apple is preventing the app from using an Apple device identifier, a random sequence of letters and numbers assigned to our iPhones and used to track our activity across apps and websites. The second is that we are telling the app developer that, by and large, we do not want our information to be tracked and in any way shared with anyone.

That seems easy. But # 2 is where things get a little complicated too.

Ad tech companies already have many ways to follow us beyond Apple’s device identifier. For example, advertisers can use a method called fingerprinting. This involves looking at seemingly innocuous features of your device – like screen resolution, operating system version and model – and combining them to determine your identity and track you across different apps.

According to data protection researchers, it is difficult for Apple to block all tracking and fingerprints taking place on iPhones. This would require knowing or predicting any new tracking method that an ad tech company is developing.

“From a tech point of view, there’s not much you can do” to stop such tracking, said Mike Audi, founder of Tiki, an app that lets you see what other apps are doing with your data.

However, the change in data protection is still significant, as we are expressly asked for consent. If we tell apps that we don’t want to be tracked and continue to do so, Apple can expel the perpetrators from the App Store.

The pop-up window also makes it easier for people to discover privacy controls, said Stephanie Nguyen, a researcher who has studied user experience design and privacy. In the past, iPhone owners could prevent advertisers from tracking them, but the tools to do that were buried in settings that most people didn’t look at.

“The option was available before, but was it really?” Ms. Nguyen said. “It’s a big change – making it visible.”

Starting this week, all apps with tracking behavior must include the App Tracking Transparency pop-up in their next software updates. That means we’ll likely see a small number of apps asking for permission to track us initially, with the number increasing over time as more apps are updated.

Apple’s new software also includes two other interesting new features: the ability to play audio with Siri using a third-party app like Spotify, and the option to quickly unlock an iPhone while wearing a mask.

For many, these will feel long overdue. Siri did seamless only worked with Apple Music for music playback since 2015 which was frustrating for those who want to use voice assistant to play songs with other music apps. The change comes because the antitrust investigation decides whether Apple suppresses competition by giving preference to its own apps.

You don’t need to change any settings for Siri to work with other audio services. If you usually listen to music using a third-party app like Spotify, over time Siri will simply find that you prefer that app and act accordingly. (Audio app developers need to program their apps to support Siri. If they haven’t already, this won’t work.) So if you always use Spotify to play music, you can say, “Hey Siri, play the Beatles ”to play a Beatles playlist on Spotify.

The other new feature helps in solving a pandemic problem. For more than a year now, wearing a mask has been especially annoying for owners of newer iPhones with face scanners to unlock the device. That’s because the iPhone camera couldn’t see our covered cups. Apple’s iOS 14.5 finally offers a mechanism to unlock the phone while in a masked state, although it does require wearing an Apple Watch.

Here’s how it works: when you scan your face and the phone finds that it can’t recognize you because your mouth and nose are blocked, it will check that your Apple Watch is unlocked and nearby. The Apple Watch practically acts as proof that you are the one trying to unlock your phone.

For this to work, update the software on your iPhone and Apple Watch and open the Settings app on your iPhone. Scroll down to “Face ID & Passcode”. Go to “Unlock with Apple Watch” in this menu and enable the option to unlock with your Apple Watch if the image scanner detects your face with a mask.

The next time you’re at the grocery store and look at your phone, your watch will vibrate once and unlock your phone. Sweet relief.