Apple introduced a pop-up window for iPhones in April that asks people for their permission to be tracked by different apps.
Google recently outlined plans to disable a tracking technology in its Chrome web browser.
And Facebook said last month that hundreds of its engineers were working on a new method of showing ads without relying on people’s personal data.
The developments may seem like technical tinkering, but they were connected to something bigger: an intensifying battle over the future of the internet. The struggle has entangled tech titans, upended Madison Avenue and disrupted small businesses. And it heralds a