Have you noticed a change to your Facebook function bar at the top (on Android) or at the bottom of your screen (on iOS)?

Various users have reported seeing changes – not just that the icons themselves become colored when you highlight them, but that the shortcuts themselves are different, with Facebook seemingly testing new variations of which buttons to show.

Turns out, it’s not a test - Facebook is actually showing each user a customized set of shortcuts on the function bar based on their individual activity. So if you use Marketplace a lot, you’ll see a Marketplace tab, if you use Watch a lot – you get what I mean.

The change was first reported by CNet late last month, but it seems to be being rolled out more widely this week, given the rise in discussion about it on Twitter.

According to CNet’s report, all users will still see the News Feed, Notifications and Menu options in their function bar, but the other slots will vary based on activity.

“At first, the icons will be chosen for you automatically based on usage, but Facebook says it eventually wants to build in settings that let people have more control over what they see.”

Facebook says different users might see anywhere between four and six icons in their personalized navigation bar, with Facebook alerting users to changes with an animated icon for each on first appearance.

So, if your Facebook feed looks different, and is different to what other people you know are seeing, you’re not special. Well, you are, but the design is now based on individual behaviors, as opposed to set variations being tested amongst specific user groups.

It’ll be interesting to see how that impacts usage – whether users are more inclined to check back more frequently on the elements they normally use, and whether usage of the elements that are dropped declines.

This could be particularly relevant in the case of Facebook Watch, which Facebook is keen to boost exposure for.