Logitech MX Master 4 mouse spotted in leak, with a new button

Logitech’s MX Master series of mice have been the gold standard for anyone who doesn’t need gaming capabilities for a while now. It’s been a couple of years since it had a major redesign, but it looks like the MX Master 4 is almost upon us, if some leaked images out of a regulator are to be believed. In addition to a mild refresh of its looks, the new mouse is packing a new thumb button.

The European Union’s Intellectual Property Office is showing off some registered designs (essentially the EU version of a design patent) granted to Logitech’s Swiss arm, revealed before an official announcement and spotted by Notebook Check. The documents don’t list the name of the product… but c’mon, that’s a next-gen MX Master mouse, or my name is Aloysius. And it’s not.

Three photos give us a look at most of the relevant angles of the device, notably missing the bottom and the charging area. The aesthetics have been adjusted a bit: The separation between the primary buttons and the main area is now on a single line, the scroll adjustment button looks easier to find, the status LED is on the top rather than the side, et cetera. The thumb buttons get the most attention, with the gesture button apparently moved from the bottom of the mouse (and activated with the side of your right thumb) much closer to the more standard buttons. There’s also a third one of those, which could be great for my Fortnite loadout.

Making an educated guess, I’d say that Logitech is going to advertise that third, slightly separated thumb button as a dedicated “AI Prompt Builder” launch button. Logitech might also offer a new and enhanced sensor in its flagship mouse — the MX Master 3S uses an 8000 DPI sensor, but some gaming mice can go way beyond that. The MX Master 3S is currently $120, after a tariff-adjacent price bump, and I’d expect a replacement model to be somewhere in the same neighborhood.

When can you get your hands on one? No idea. But since these look like fairly complete promotional images, I wouldn’t be surprised to see the new mouse launch before the back-to-school rush in the fall.