Facebook and Apple are in a fight. Your browsing history is in the center.

Apple and Facebook will need each other in the long run, because billions of people want their social media apps to work well on their phones and tablets. But first, the two Californian tech giants must settle a brawl that’s unfolding in newspaper ads, industry meetings, and potentially in federal court.

Facebook on Thursday ran its second full-page newspaper ad in as many days, attacking Apple’s plans to notify iPhone and iPad users when apps are tracking them online.

“Apple plans to roll out a forced software update that will change the Internet as we know it, for the worse,” Facebook said in the announcement.

It is a high-risk and unusually personal struggle between two companies that have far-reaching influence. At the heart of the battle is how the advertising-dependent part of the internet will function for years to come.

In the coming weeks, Apple plans to roll out a new feature on its devices that will alert people when an app like Facebook is trying to “track your activity on other companies’ apps and websites.” People will have options like “Ask app not to monitor” or “Allow”.

“Users should know when their data is being collected and shared between other apps and websites, and they should have the ability to allow it or not,” Apple said in a statement. “App Tracking Transparency in iOS 14 doesn’t require Facebook to change its approach to tracking users and creating targeted advertising, it just requires them to give users a choice.”

For Facebook, the possibility that many people disallow tracking threatens one of the streams of data that make its advertising business so profitable. Facebook uses data such as your browsing history to show people the ads they are most likely to want to see and to show marketers that its ads are working.

“Apple’s move isn’t about privacy, it’s about profit,” Facebook said in a statement. He argues that Apple has an edge if more Internet becomes subscription-based, because Apple collects fees from its app store.

The two companies, based within a 15-minute drive of each other, have been around suspicious for years. Apple CEO Tim Cook criticized Facebook for “collecting bits of personal data,” while Facebook CEO Mark Zuckerberg responded by calling iPhones an expensive product for the world’s elite, not the masses. Facebook encourages its employees to use rival Android devices.

Last year, Apple wreaked havoc on Facebook’s headquarters by blocking Facebook employee access to Facebook’s internal business apps running on iPhones. Apple had ruled that Facebook improperly paid teens and others for smartphone data.

Companies have radically different business models. Last year, Facebook earned $ 70 billion from advertising, almost its only source of revenue. Advertising sales are a small part of Apple’s $ 275 billion annual revenue, which comes mostly from device sales and app store fees.

Apple said new tracking notifications will begin appearing in early 2021. Privacy groups like the Electronic Frontier Foundation support them.

But Facebook is making one last attempt to get Apple to back down or compromise with industry standard setters. With offline ads in newspapers like The Washington Post and The Wall Street Journal, the social networking company is looking to take its side. the millions of small businesses that buy ads on Facebook and Instagram.

The latest announcement, Thursday, claims that free online publishers won’t be able to survive if Apple gets its way, unless publishers charge for subscriptions – which Apple could get a slice of, thanks to the rules in its app. store.

“Grab your favorite cooking sites or sports blogs. Most are free because they show advertisements,” Facebook said in its ad. “Apple’s change will limit their ability to serve personalized ads. To make ends meet, many will have to start charging you subscription fees or adding more in-app purchases, making the Internet much more expensive and reducing high-quality free content. “

Facebook raised the prospect of an antitrust lawsuit. A blog post claims that it has pledged to provide information to a federal court in an ongoing lawsuit against Apple filed by Epic Games, which is seeking to reduce the fees it pays through Apple’s app store.

“We believe Apple is acting anti-competitive by using control of the App Store for the benefit of its bottom line at the expense of app developers and small businesses. We continue to explore ways to address this concern, “Facebook said.

Facebook is fighting antitrust complaints from states and the Federal Trade Commission, and both Zuckerberg and Cook have been compared to “emperors”.

Apple, for now, is sticking to its notification monitoring plans and points to a long history of advocating for online privacy.

“We believe this is a simple matter of defending our users,” Apple said.