That doesn't say whether they are using an app on mobile or just a mobile browser. The app is (was? I haven't used it in ages) a notorious energy-hog that will drain your battery.

Unfortunately I can't find numbers that break down mobile site vs. native app use.

Judging by how poorly maintained and how rarely updated the mobile site is, I think it's safe to assume that the vast majority of people are using the native apps, not the mobile site. Major features like the marketplace and video tabs are nowhere to be seen on the mobile site, for example. If the mobile sites were getting the bulk of users, Facebook would surely prioritize it.

I don't think that's safe to assume at all. A lot of phone users (think mostly older people) still don't really know what an app store is. I don't have any numbers, but from seeing how 'ordinary' people use their phones, I wouldn't make any assumptions about preferring apps.

As for facebook's priorities - they could surely also be neglecting the mobile site with the aim of getting people to install and use their app. Again, I don't know if this is the case, but it's certainly plausible.

I think that might have been true in 2009. It's far from true today.

I just noticed this FB blog post: https://developers.facebook.com/ads/blog/post/2018/05/09/rel.... The chart at the top shows app vs. web use of mobile devices, not just for FB but overall. As I expected, mobile web is significantly smaller than native apps, from a time-spent standpoint.

Agreed. I haven't used the app in years. Instead I use mbasic.facebook.com. When I check the demographics Facebook puts me in for advertisers, I'm categorized as a "mobile user".