Facebook Does Something New: L.Facebook.com and LM.Facebook.com

We just noticed a new referral source in our Analytics data. In the past we have seen two referral sources from Facebook – plain “facebook.com” and mobile “m.facebook.com.” Just in the past few days we’ve noticed two new ones – “l.facebook.com” and “lm.facebook.com” – and we’re not completely sure what they are yet.
From what we can see so far, they first appeared on April 5th and the numbers were small on both the 5th and 6th. They’ve grown significantly in the last few days.

The vast majority of visits from l.facebook.com are desktop users, with some tablets and nearly zero mobile. This is in stark contrast to our overall site traffic, which is roughly 60% mobile. Not surprisingly, the lm.facebook.com users are almost entirely mobile, with a few tablets.


We occasionally do sponsored posts so we considered the possibility that the new referrer was related to such ads. Since many of the landing pages were not related to sponsored posts, we reject that hypothesis.
The users are evenly split between new and returning visitors, which is roughly consistent with overall site usage, so it’s not anything to do with that.

Gender, age and other demographics also seem consistent with general site traffic. In short, we don’t see any patterns that show how l.facebook.com and lm.facebook.com are different from regular facebook.com and m.facebook.com. At least not yet. We searched both Google and Bing to see if we could find any explanations and we found nothing.
One possibility may have to do with “shared logins” or social logins where the user may be finding us on a third-party site while logged in to that site through Facebook. When we tried to go to l.facebook.com on our browsers we simply got switched over the regular facebook.com. But interestingly when we tried going to lm.facebook.com on a browser we saw this:

We’ll keep looking at it and will update if we figure something out. Please post comments if you think of anything.