Here are some of the monthly active user statistics for various social media platforms, according to the search results:

1. Facebook - 2.96 billion monthly active users (MAUs) [1]
2. YouTube - 2.56 billion MAUs[2]
3. WhatsApp - 2 billion MAUs[3]
4. Instagram - 2 billion MAUs[3][4]
5. WeChat - 1.26 billion MAUs[2]
6. TikTok - 1 billion MAUs[2]
7. Facebook Messenger - 988 million MAUs[2]
8. Snapchat - 557 million MAUs[2]
9. Pinterest - 444 million MAUs[2]
10. Twitter - 368 million MAUs[5]

It's worth noting that these numbers are subject to change and may vary depending on the source. Additionally, there are many other social media platforms with significant user bases that are not listed here. When choosing which social media platforms to use for your brand, it's important to consider the relevance to your target audience and the quality of engagement on each platform, rather than just the number of users.

Citations:

[1] https://buffer.com/library/social-media-sites/

[2] https://www.semrush.com/blog/most-popular-social-media-platforms/

[3] https://datareportal.com/social-media-users

[4] https://statusbrew.com/insights/social-media-statistics/

[5] https://en.wikipedia.org/wiki/List_of_social_platforms_with_at_least_100_million_active_users