FBCLID is "Facebook Click ID". It is sent to third party sites as a URL parameter so that if an advertiser complains about fake clicks or something they can provide the IDs and the Facebook advertising team knows which ones they are talking about.

Analytics companies (I think Google and a few others) can pay Facebook to get data on your behalf like what page it came from and the demographics of the visitor.

Google AdWords does this as well on paid clicks with GCLID

This is terrible. Someone with access to server logs at a few web sites (or someone that loads a third party resource (ads, analytics, sharethis buttons, etc) onto a few web sites) would be able to know exactly who is coming from fbook and viewing different types of content.. no inside access to fbook or their data required.

I can't believe nothing is auto-stripping this url addition between firefox and ublock origin - must find and tell others.

Note that the ID changes for each "click" - hence "Facebook CLICK ID" - so you can't tie different clicks back to the same user without access to Facebook's data.

But yes, an extension to strip these (along with `gclid` from Google, `reddit_cid` from Reddit, and so on) would be very welcome.

thanks for this - I was confused about it since I have seen a few that looked very similar (first 12 characters of it the same) - did a quick, slightly deeper check into history and see that I do have 2 urls that have the exact same string, but it appears at least in this one case, that it's a click to a short link that forwards (dj-m.ag to djmag dot com) - so the similarity was confusing, and see some doubles freaked me out. now I see at least some differences in several - so I guess unless there is an easy pattern match, or as the title of this hn thread story suggests they may be able to reverse engineer fbook clicks - it's highly concerning to be sure since so many places use third party scripts and assets.

fingers crossed this is good and it gets better.

I've seen this tracking param when people shared with me some links, which they got from Fb.

There is a Firefox extension ClearURLs, which strips some tracking parameters from the url.

From what I remember, if you click in Fb on a link, it redirects first to an internal tracking url, and then to your final link. This is not limited to Fb only.

Yeah, this sort of thing is far from unique to Facebook, and is why it's been my practice for many years to never just click on a link. Instead, I copy it so I can strip out all of the unnecessary decorations and trackers before browsing to it.

Probably a http request tracking ID that can be used for debugging the request.

It's a "Facebook click ID" and it's likely intended to evade Safari's "Intelligent Tracking Prevention" on third-party cookies.

This. We knew this was coming when Safari added that.