The Apple Watch Series 12 is a millimeter wider, and the screen didn't grow

The Apple Watch Series 12 is a little wider than the watch it replaces, and the screen didn't grow to match. That's the finding from 9to5Mac, which read the case measurements on Apple's own website. Apple didn't mention the change when it announced the watch.

The 42mm Series 12 measures 42mm by 37mm. The Series 11 and Series 10 both measured 42mm by 36mm. The 46mm Series 12 is 46mm by 40mm, against 46mm by 39mm on the last two models. The height is the same. The width went up by a millimeter.

The display did not change at all: according to Apple's comparison page, as 9to5Mac reports it, all three generations share the same screens, 374 by 446 pixels and 970 square millimeters on the 42mm, and 416 by 496 pixels and 1196 square millimeters on the 46mm.

Put those together and you get a bigger frame around the same picture. The bezels are thicker.

The iPhone, the iPad, the Mac and the Watch have all shrunk their borders, generation after generation, to make the screen look like it runs to the edge. A thicker bezel is a rare step the other way, and it runs against about a decade of Apple design.

9to5Mac's reading is that the new internals need room, pointing to what Apple calls the Health Sensing System. That's a sensible guess. It is also a guess. Apple hasn't said why the case grew, and a millimeter of width is exactly the kind of thing a company changes for reasons it never explains.

A millimeter barely matters on paper. On a wrist, maybe. A watch is an object you look at dozens of times a day, and a border you never noticed on your old one can be the first thing you see on the new one. If you're coming from a Series 10 or 11, expect the new watch to look a touch less edge to edge, even though you aren't losing a single pixel.

There are two practical questions this raises, and neither is answered yet. The first is bands. A millimeter of width is small enough that existing bands should still fit the lugs, but that's worth checking before you assume. The second is cases and screen protectors. Anything cut tightly for the older dimensions may not sit right on the new one.

If you're buying your first Apple Watch, none of this matters. You'll never see the old bezel. If you're upgrading, go look at one in a store before Friday. The change is small, and it's real.