While you probably shouldn't overuse this style, you may want an element or two on your designs to blur the background behind them.
And it's incredibly simple in Adobe XD. On this landing page, I may want the navigation bar to show a glimpse of the images behind it. And while I could just drop the opacity a touch, I'm feeling fancy. With the layer selected, I'll check on Background Blur in the properties inspector and then adjust the sliders to get the exact result that I'm looking for.
The first slider controls the amount of blur. The second is for brightness. And the third, opacity. Now that the navigation bar is looking quite nice. It's time to apply the blur to all the others.
Of course, if I was using symbols, changes would apply automatically, but I wanted to show you one more tip. Copying the current layer — with command or Control + C — I'll now select all the others. I can do this by holding down command or CTRL + Shift and clicking the others I wish to select. Once selected, right-clicking on any of them will let me paste the appearance of the copied layer. Applying the blur to all my navigation bars.
With the blurs now in place, previewing my prototype will let me see it in action and you'll notice that as I click through the various screens, the blur beautifully renders behind the navigation bar.
And that's your bite-sized look at Background Blurs in Adobe XD.