By MAU, 2.3 billion vs 1.9 for YouTube (arguably not a messaging-based SM site), and 1.0 for Instagram (owned by FB). Qzone is 4th at 563 million, 17% of FB+Insta.

Not quite 90% by that measure, but close.

https://www.dreamgrow.com/top-15-most-popular-social-network...

Mindshare, reach, time-on-site, and media references are alternate measures. Definitions matter.

Eh, I guess this is not true. To me, 'social media' always meant websites like MySpace and Orkut where friends connect, and not just 'website where users can communicate in some way' a la Pinterest/Reddit/YouTube.

But I realise now that isn't the right definition... still not sure what the word is for the Friendster/MySpace clones--but among those I am pretty sure Facebook is more than 90% of the market (outside of China), possibly more than 99% with Google+ closing.

Remember that Facebook owns Instagram and Whatsapp.

They might not be 90+ everywhere, but they do own a significant amount

Instagram and whatsapp are facebook. Ofc, even then 90% might be too much.