KEY POINTS
  • Amazon's ad business is still growing, but not as quickly as it was growing last year. 
  • The tech company has quickly become a contender to take on the Google and Facebook duopoly that has dominated the digital advertising ecosystem.
  • Advertisers are thinking more carefully about which platforms provide the highest amounts of sophistication and return on investment.
Jeff Bezos, Chairman and CEO of Amazon, speaks at the George W. Bush Presidential Center's Forum on Leadership in Dallas, Texas, U.S., April 20, 2018.

Amazon's ad business is still growing at a healthy clip. But the huge growth rates that came in recent quarters have cooled as advertisers seem to begin spending more carefully on the platform.

Amazon, which reported its Q1 2019 results Thursday, said its "other" segment consisting primarily of advertising sales slowed to 36% in the first quarter from the previous year, at $2.72 billion. On an adjusted basis, the year-over-year growth rate in that "other" segment in Q4 2018 was 38%, and ranged between 51% and 73% in previous quarters last year. Some say, though, it's only a matter of time before growth amps up again.