Facebook’s ad revenue was up more than 45 percent during the first three months of 2021, soaring to $25.4 billion — or about seven times what Twitter makes in an entire year. But the company sees some potential problems on the horizon that could limit continued growth: regulators are closing in on ad tracking practices, and a feature launched this week by Apple could harm its ability to target ads.

“We continue to expect increased ad targeting headwinds in 2021 from regulatory and platform changes,” Facebook CFO Dave Wehner writes in the company’s Q1 2021 earnings release. Wehner specifically calls out iOS 14.5, which includes a feature that lets iPhone and iPad users easily stop apps from tracking them in certain ways. Facebook expects to start seeing an impact from the changes to iOS right away.

Facebook believes its ad revenue will continue to grow over the rest of 2021 even with those changes, but it sees a slowdown coming in the second half of the year. Mostly, Facebook says, that’s because it did so well last year during the pandemic. But regulatory factors and Apple’s changes will play a role.

The new update requires apps like Facebook to proactively ask users to consent to being tracked for the purpose of advertising. Facebook has criticized the feature as a threat to the businesses that rely on those ads. “Apple’s latest update threatens the personalized ads that millions of small businesses rely on to find and reach customers,” a Facebook website reads.

On a call with investors, Facebook executives said the company was working on improvements to its ad tech that would allow for better ad targeting even with access to less data. Facebook COO Sheryl Sandberg framed it as a “rebuilding” of the company’s tech; Wehner said Facebook was “making progress” on solutions with the goal to “maintain and even improve performance” in the long run.