Facebook has the largest user base among major social media platforms, with over 3 billion monthly active users in the sources I found.

Quick Scoop

  • Largest platform: Facebook.
  • Why it leads: It remains the most used social network worldwide by monthly active users.
  • Close followers: YouTube and WhatsApp also have enormous audiences, each with around 2 billion or more users.

Popularity Snapshot

Platform| User base| Source
---|---|---
Facebook| 3.07 billion monthly active users| 1
YouTube| 2.504 billion monthly active users| 1
WhatsApp| 2 billion monthly active users| 1
Instagram| 2 billion monthly active users| 1
TikTok| 1.582 billion monthly active users| 1

Bottom line

If you mean the single biggest social media platform by user count, the answer is Facebook.