Google Inc. and other advertising companies have been bypassing the privacy settings of millions of people using Apple Inc.'s Web browser on their iPhones and computers—tracking the Web-browsing habits of people who intended for that kind of monitoring to be blocked.

The companies used special computer code that tricks Apple's Safari Web-browsing software into letting them monitor many users. Safari, the most widely used browser on mobile devices, is designed to block such tracking by default.

...