I recently noticed that when Firefox focuses on the address bar, it expands the address bar. I thought this had a UI / UX benefit as it was a visual change. However, no literature was found on them.
Is there a UI / UX benefit to this change? Since this was an indication method that is rarely seen in general input fields, I would like to know the advantage of using this method.
I'm not sure there's a real benefit; the animation will draw the user's attention but since they just clicked on the address bar, that's not necessary. The Firefox 'Megabar' seems to be inspired by the "Reborn 3" bar of the Opera browser which has the additional benefit of dimming the page content which is potentially distractive when navigating/searching (see below). But the Firefox bar has no such benefit, and there's a reason this question on our sister site Super User: How to disable address bar expansion in Mozilla Firefox 75? has 82 upvotes at the time of writing.
source: askvg.com
I think one of the benefits is more of a visual one. The interface is putting more focus on the address bar and is creating more space around it when focused and minimising it when that is not needed.
The UX benefit of this approach that I can see is that it's making it easier and clearer for the user to understand which part if focused and what it's the focus not on the page.
Personally, I don't this is such a bad idea, I like having this micro interactions on interfaces. I think it makes them more playful and reactive to the users' actions.
