Are you curious about which social media sites people use according to an age demographic?
Pew Research Center has provided the breakdown by age for American adults in 2021.

YouTube and Facebook are the most popular online platforms, and their user bases are most representative of the population as a whole.
Even though other platforms don’t match the overall reach of YouTube or Facebook, there are certain sites or apps, such as Instagram, Snapchat, and TikTok, that have a particularly strong following among young adults. A majority of 18- to 29-year-olds use Instagram (71%) or Snapchat (65%), while roughly half use TikTok. They stand in stark contrast to those of older age groups. While 65% of adults ages 18 to 29 report using Snapchat, just 2% of those 65 and older do so – a difference of 63 percentage points.
Visit Pew Research Center to read the data in full