Facebook, as of its most recent earnings, reported 2.91 billion monthly active users after seeing 6% year-over-year growth. And recently, Instagram employees leaked its network had surpassed 2 billion monthly users, up from the 1 billion monthly user milestone reported in June 2018.

However, Insider Intelligence’s forecast is referencing its own 2022 predictions, which uses a slightly different set of calculations. The firm has its own definition of a monthly active user that may differ from those of each company it analyzes. For example, it only counts users who log in at least once a month consistently over a calendar year period, and it attempts to weed out the fake accounts from its estimates. This is meant to provide clients with a more consistent “apples to apples” comparison across all platforms.

According to the firm’s estimates, Facebook will reach 2.1 billion monthly users in 2022, followed by Instagram with 1.28 billion users. TikTok will follow with its 755 million monthly users, ahead of Snap and Twitter.

TikTok, over the past couple of years, has been growing quickly.

App intelligence firm Sensor Tower reported the short-form video app crossed 2 billion downloads across the App Store and Google Play in the first quarter of 2020. A separate report by App Annie later found TikTok saw 325% growth in 2020, and the monthly time spent per user also grew faster than any other app — including by 65% in the U.S., surpassing Facebook.

In July 2021, Sensor Tower noted TikTok (including sister app Douyin in China) had become the first non-Facebook mobile app (outside of games) to reach 3 billion downloads globally across the App Store and Google Play, while TikTok consumer spending surpassed $2.5 billion globally. This put the app in the company of only a handful of others that had reached that milestone, including Tinder, Netflix, YouTube and Tencent Video.

While other firms had predicted TikTok’s monthly active user base would top 1 billion in 2021, Insider Intelligence’s forecast is a bit more conservative due to its methodology. But it does expect the app to continue to grow, if at a slower rate of 15.1% in 2022.

As a result of its growth, TikTok’s share of overall social networking users is also climbing upwards. Insider Intelligence’s forecast believes TikTok will surpass a 20% share for the first time and will approach a one-quarter share by 2024.

“The rise of TikTok is especially challenging for Snapchat, with which it competes head-to-head for the youth audience,” remarked Insider Intelligence principal analyst, Debra Aho Williamson. “Although TikTok does not share much similarity to Twitter, its massive size relative to the more-established platform is a clear reflection of the addictive nature of TikTok’s content,” she said.

There’s still plenty of room for TikTok’s future growth, the firm also pointed out, as next year, 3.57 billion people will use a social networking app at least once per month.