Facebook's stock showed volatility in after-hours trading Wednesday, despite adding users and beating on top and bottom lines.

Why it matters: Investors seem spooked by proposed changes to user data collection by Apple that would impact Facebook's ad business, in addition to perennial threats of new federal privacy regulations.

Details: In a statement, Facebook addressed the Apple changes and said ad targeting headwinds in 2021 include "the impact of platform changes, notably iOS 14, as well as the evolving regulatory landscape."

• The company says it expects to see an impact from the changes "beginning late in the first quarter."
• While Facebook beat Wall Street estimates on overall user growth, it reported for the second straight quarter daily active user declines in North America, its most lucrative ad market. But the company lost 1 million daily active users in the U.S. and Canada last quarter, it gained 3 million monthly active users in that same period.

By the numbers, per CNBC:

• Earnings: $3.88 per share vs $3.22 per share forecast by Refinitiv
• Revenue: $28.07 billion vs $26.44 billion forecast by Refinitiv
• Daily active users (DAUs): 1.84 billion vs 1.83 billion forecast by FactSet
• Monthly active users (MAUs): 2.8 billion vs 2.76 billion forecast by FactSet

The big picture: Facebook's business was resilient in the fourth quarter despite pandemic-related headwinds to the advertising sector broadly.

• In a statement, the company attributed its growth to two broad economic trends playing out during the pandemic: the ongoing shift toward online commerce and the shift in consumer demand to products and away from services.

What's next: Facebook forecasts that in the first quarter of 2021, it will be "lapping a period of growth that was negatively impacted by reduced advertising demand during the early stages of the pandemic."

Go deeper:

• Facebook's Q3 2019 earnings
• Facebook Q2 2020 earnings
• Facebook's Q1 2020 earnings
• Facebook's Q4 2019 earnings