The shares of Meta Platforms plunged more than 20% after the social media company posted a weaker-than-expected forecast, blaming Apple's privacy changes and increased competition for users from rivals like TikTok.

Facebook's global daily active users declined from the previous quarter for the first time, to 1.929 billion from 1.930 billion.

Meta said it faced hits from Apple Inc's privacy changes to its operating system, which have made it harder for brands to target and measure their ads on Facebook and Instagram. It also cited macroeconomic issues like supply-chain disruptions.

The tech giant also faces pressure from platforms like TikTok and Google's YouTube, said it expected slowing revenue growth in the coming quarter due to increased competition for users' time and a shift of engagement toward such features as its short video offering Reels, which generate less revenue.

The after-hours slump in Meta shares vaporized $200 billion of its market value, while peers Twitter Inc, Snap Inc and Pinterest Inc lost another $15 billion in value.

Meta, owner of the second-largest digital ad platform in the world after Google, had previously warned its advertising business faced "significant uncertainty" in the fourth quarter.

Meta's chief financial officer, Dave Wehner, told analysts on a conference call that the impact of Apple's privacy changes could be "in the order of $10 billion" for 2022.

Apple's changes to its operating software give users the choice to prevent apps from tracking their online activity for ads, making it harder for advertisers that rely on data to develop new products and know their market.

"I'm encouraged by the progress we made this past year in a number of important growth areas like Reels, commerce, and virtual reality, and we'll continue investing in these and other key priorities in 2022 as we work towards building the metaverse," CEO Mark Zuckerberg said in the earnings release.