Google said in January that it would eventually strip third-party trackers, or cookies, from its Chrome browser, a decision it described as an effort to build “a more private web.” But the American Association of Advertising Agencies and the Association of National Advertisers quickly complained in an open letter that removing cookies could “choke off the economic oxygen from advertising that start-ups and emerging companies need to survive.”

The reaction to the recent search page changes was so negative that Google took the rare step of reversing some of the design changes last week. In a statement, Google said it was “experimenting with a change” to the new logos next to the unpaid links, although it did not alter the new ad logo.

Lara Levin, a Google spokeswoman, said in a statement that the recent design changes mirrored a new look the company introduced for search results on mobile phones in May. The company tested the new look on desktop search, and the results were positive, she said, but it decided to make some changes to respond to “feedback from users.”

Alphabet, Google’s parent company, is expected to report next week that annual revenue topped $150 billion in 2019. But Google’s ad business is under growing pressure from rivals like Amazon and Facebook.

Money from Google advertising accounts for about 80 percent of Alphabet’s revenue. Search advertising is essential to the future of Google, though the company does not say how much it makes on it alone. Magna, a media intelligence firm, estimates that overall search advertising increased 14 percent in 2019 to $144 billion.

Google constantly tinkers with the design of its search results page, and its once bare-bones approach to search results — characterized as “10 blue links” — has changed drastically in recent years. The company once tested 41 shades of blue to find which one users liked best, and it has steadily made its search ads more inconspicuous over time.