A new type of ad is heading for your iPhone

ONLINE SHOPPERS often feel they are being watched. Put an item in your basket but fail to buy it, and it may follow you plaintively around the internet for days. Announce your engagement on social media and you will be hit with adverts for the honeymoon. As you turn 40, expect the attention of elasticated-trouser merchants.On April 26th Apple, which supplies one-fifth of the world’s smartphones and around half of America’s, introduced a software update that will end much of this snooping. Its latest mobile operating system forces apps to ask users if they want to be tracked. Many will decline. It is the latest privacy move forcing marketers to rethink how they target online ads.