
The size and opacity of the shadow doesn’t change in the move to Big Sur, even as windows themselves get a hint brighter and flatter. Window shadows work the same way they do in Catalina-all windows have a light shadow surrounding them, and the active window has a slightly deeper and more noticeable shadow under them. Windows in general are brighter than in Catalina, with lighter title bars (for apps that have them). The first thing you’ll notice about Big Sur windows is that Catalina’s gently rounded corners have become even rounder, closer to the corners of an iPhone X or late-model iPad Pro screen (Mac screens don’t have rounded corners yet, but no one should be surprised if it happens in some future Apple Silicon Mac). Windows need to be able to show alerts and prompts and file pickers when necessary. An important distinction between macOS and iPadOS is the Mac’s windowed multitasking, which calls for stronger use of shadows (to show what is on top of what) and a clear delineation between active and inactive app windows. Let’s begin with the basics: the way that app windows overlap and interact on-screen. Overall, Big Sur feels familiar, but not all the changes will be to everyone’s taste. In others, it remains visually and functionally identical to Catalina. In some ways, Big Sur changes the fundamental look and feel of the Mac more significantly than any update since the early days of Mac OS X. Big Sur makes the Mac a bit more iPad-y without making it not the Mac. Those changes have added Mac-ish flourishes to the iPad without making it not the iPad. You could also compare it to the way Apple has developed iPadOS in the last two or three years-adding a dock, improving multitasking, and implementing more robust keyboard and mouse support.

If post-Yosemite macOS releases set that slider at around a four, Big Sur dials it up to around six.

If you’ve been using Macs for a long time, imagine a slider that goes from one to ten, with “Snow Leopard” at one and “iPad OS” at ten. There are two ways to think about how Big Sur changes the Mac’s look and feel.
