When Safari 11 arrives on iPhones and Macs later this month, Apple's browser will come with a feature called Intelligent Tracking Prevention that makes it harder for advertisers and publishers to track what you do online.

Surprise! Advertisers hate it.

Six advertising groups published a letter Thursday asking Apple to "rethink" the technology, warning that it will "sabotage the economic model for the internet." The argument boils down to this: If advertisers can't personalize ads, then free services like Facebook and YouTube and Imgur will have to find some other way to make money to survive. (See below for the full text of the letter.)

The Safari feature is the newest serious threat to an industry that's funded the growth of tech titans like Google and Facebook. Ads are indeed core to the internet, but they slow down web pages, suck power out of our batteries, eat through our monthly data plans and fill websites with distractions.

Ad blockers are on the rise -- even within Google's Chrome browser. And even if browsers don't block the ads themselves, blocking ad tracking means browsers can improve your privacy online.

Apple has been trying hard for years to make privacy a selling point for its products. "Safari is [the] best ally of Brave among big-four browsers on privacy," tweeted Brendan Eich, founder and CEO of browser maker Brave, whose eponymous browser blocks ads and ad tracking software on websites.

Browser makers including Mozilla and Microsoft tried to get the ad industry to voluntarily support a technology called Do Not Track that would let you declare you didn't want your online behavior recorded. The ad industry didn't like it, and the effort fizzled. Now browsers -- called user agents in technology circles because of their role in representing you to the internet -- are becoming more assertive. They're more selective now about which website code actually makes it to your screen, PC and phone.

Cookie crunch

The advertising group's letter involves Safari's handling of a decades-old technology called cookies. Browsers store and analyze these small text files to keep track of things like what items you've put in your e-commerce shopping cart, what your preferred language is and whether you're logged into Gmail. Advertisers can use their own cookies to figure out, for example, that you looked up waffle iron prices or spend hours a week on a forum for coin collectors.

When you visit a website, your browser can store two types of cookies: first-party cookies, which are from the publisher of the website, and third-party cookies, from companies such as advertisers that want to know if you've seen their ads on that website.

Browsers are increasingly cracking down on third-party cookies. The Safari and Brave browsers block third-party cookies, and for years you've been able to configure other browsers like Microsoft Edge, Google Chrome and Mozilla Firefox to block.

Safari 11 -- which arrives on Sept. 11 for iPhones and iPads and Sept. 25 for Macs with the new MacOS High Sierra software -- goes a step farther, though. Its intelligent tracking-prevention technology makes it harder for ads to follow you around from one site to another and for advertisers to keep track of your browsing habits over the longer term. One part of the approach is deleting even first-party cookies if it's been more than 30 days since you interacted with the website that set the cookie.

Sabotage the net

That's what's got advertising groups squealing.

"Apple's Safari move ... will hurt the user experience and sabotage the economic model for the internet," the letter said. "Apple's unilateral and heavy-handed approach is bad for consumer choice and bad for the ad-supported online content and services consumers love. Blocking cookies in this manner will drive a wedge between brands and their customers, and it will make advertising more generic and less timely and useful."

The groups signing the letter were the American Association of Advertising Agencies (4A's), the American Advertising Federation (AAF), the Association of National Advertisers (ANA), the Data & Marketing Association (DMA), the Interactive Advertising Bureau (IAB) and the Network Advertising Initiative (NAI).

If you fear Safari 11 will drive a wedge between you and your favorite brands, you can disable intelligent tracking prevention through Safari's preferences.

Facebook subscription?

Nobody wants to start paying for a Facebook subscription. But the advertisers probably shouldn't expect us to leap to their defense. Seventy-nine percent of people surveyed would reject a website request to share their browsing behavior with an advertiser and its analytics partners, according to a study by PageFair, which sells software to try to thwart ad blocking.

The ad groups might want Apple to back down, but it's pretty clear where Apple stands. It announced Intelligent Tracking Prevention at a major keynote speech in June, to audience applause, and showed it's thinking of the internet broadly, too.

"The success of the web as a platform relies on user trust," Apple Safari engineer John Wilander said in a June blog post about Intelligent Tracking Prevention. "Many users feel that trust is broken when they are being tracked and privacy-sensitive data about their web activity is acquired for purposes that they never agreed to."

Here's the letter in full:

September 14, 2017

An Open Letter from the Digital Advertising Community

The undersigned organizations are leading trade associations for the digital advertising and marketing industries, collectively representing thousands of companies that responsibly participate in and shape today's digital landscape for the millions of consumers they serve.
We are deeply concerned about the Safari 11 browser update that Apple plans to release, as it overrides and replaces existing user-controlled cookie preferences with Apple's own set of opaque and arbitrary standards for cookie handling.

Safari's new "Intelligent Tracking Prevention" would change the rules by which cookies are set and recognized by browsers. In addition to blocking all third-party cookies (i.e. those set by a domain other than the one being visited), as the current version of Safari does, this new functionality would create a set of haphazard rules over the use of first-party cookies (i.e. those set by a domain the user has chosen to visit) that block their functionality or purge them from users' browsers without notice or choice.

The infrastructure of the modern internet depends on consistent and generally applicable standards for cookies, so digital companies can innovate to build content, services, and advertising that are personalized for users and remember their visits. Apple's Safari move breaks those standards and replaces them with an amorphous set of shifting rules that will hurt the user experience and sabotage the economic model for the internet.

Apple's unilateral and heavy-handed approach is bad for consumer choice and bad for the ad-supported online content and services consumers love. Blocking cookies in this manner will drive a wedge between brands and their customers, and it will make advertising more generic and less timely and useful. Put simply, machine-driven cookie choices do not represent user choice; they represent browser-manufacturer choice. As organizations devoted to innovation and growth in the consumer economy, we will actively oppose any actions like this by companies that harm consumers by distorting the digital advertising ecosystem and undermining its operations.

We strongly encourage Apple to rethink its plan to impose its own cookie standards and risk disrupting the valuable digital advertising ecosystem that funds much of today's digital content and services.

Signed,

American Association of Advertising Agencies (4A's)
American Advertising Federation (AAF)
Association of National Advertisers (ANA)Data & Marketing Association (DMA)
Interactive Advertising Bureau (IAB)Network Advertising Initiative (NAI)