Apple mobile iOS devices (iPads, iPhones, and iPod Touches) are used by 130 million people, but they present a huge blindspot to advertisers. All Apple mobile devices use the Safari browser, as do millions of Apple laptop and desktop computers. Safari blocks third-party cookies by default, which is good for privacy and good for consumers. But it is bad for advertisers who rely on browser cookie tracking to measure the effectiveness of their ads. Marin Software , which offers a way to manage paid search advertising, conducted a study it provided to TechCrunch which shows that 80 percent of the time iOS devices don't count paid-search conversions (i.e., clicks) because cookie-tracking is turned off. On the Mac, the undercounting occurs 50 percent of the time. All told, when you count all browsers, 38 percent of all paid-search clicks are not being counted.