Google and Meta Are Losing Their Grip on the Digital Ad Market

For more than a half-decade, Alphabet Inc. and Meta Platforms Inc. have ruled the digital advertising market—the money machine that funds the modern internet. They’ve collected more than half of all online ad dollars, year after year, to the point that competitors and regulators feared there would be no realistic way to break their hold.

This year the duo will have some of their biggest challenges yet, facing competition that’s fiercer and better-funded than it’s been in a decade. Alphabet and Meta are still trying to recover from a change in Apple Inc.’s privacy policy that crippled the ...