Safari Is Now The Only Major Browser That Offers ‘Do Not Track’ on iOS

On Wednesday, Google released a new version of its popular Chrome browser for Apple iPhones and iPads promising faster speeds and fewer crashes.

But some privacy-conscious users got a bad surprise when their apps got upgraded (Google is rolling out the upgrade "gradually"). All of a sudden, their iPhone Chrome browser stopped supporting "Do Not Track," a feature designed to help consumers opt out of online tracking.

Snap. I just launched today's Chrome update to iOS and was given this message. What is Google up to??? Jason KintJanuary 28, 2016

Chrome on iOS is no longer able to send the Do Not Track header! (due to changes in iOS, it seems) Joseph Lorenzo HallJanuary 28, 2016

On Chrome's support page, Google writes that "because of iOS constraints" some features normally offered in Chrome for other platforms won't be available on iPhones and iPads, including "Do Not Track."

This means that if you're an Apple user, your options to stop websites from tracking you as your surf the web on your cellphone or tablet are dwindling. You can use Safari, where Do Not Track is still an option, and where you can use content blockers. (content or ad blockers are not available for third party browsers right now) Otherwise, you are left with incognito mode on the other browsers, or you have to use separate apps such as VPNs.

"[It's] not easy," Joseph Hall, the chief technologist with the Center for Democracy and Technology, told me in an online chat. "This is one of the misfortunes of mobile internet. One does not have the same tracker blocking options as on desktop [operating systems]."

The reason why Chrome stopped supporting Do Not Track is because Chrome on iOS now uses Apple's new(ish) WKWebView API. This platform, even though it's the same one Safari is built on, restricts several functionalities for third-party browser developers.

"From a technical point of view, this is Apple's 'fault,'" Arvind Narayanan, an assistant professor of computer science at Princeton who has worked on developing Do Not Track, told me in an email. "If the API in question doesn't expose that functionality, there's nothing Google or Mozilla can do about it."

Normally, browsers add a Do Not Track request in the header field, demanding websites not to track the users. It's worth remembering that while some companies have pledged to honor Do Not Track requests, sites can ignore the request (and many do).

On Apple's WKWebKit third-party developers like Google don't have the ability to change or add HTTP headers and thus enable the Do Not Track request, as Google itself complained in a bug report in early 2015. For the same reason, even Mozilla's FireFox browser, historically the most pro-privacy browser out there, doesn't offer Do Not Track on iOS. In fact, a Mozilla developer also complained about it in a message to an internal mailing list.

Apple, as well as Google, did not respond to a request for comment.

Google wrote in its support page that "if Apple makes changes to WKWebView to allow these features, we will add them back in." Until then, Chrome users on iOS are out of luck.