A Galaxy S21 inside mouse hardware is precisely what one builder has achieved, cramming a functioning Samsung smartphone into the shell of a wireless mouse and running it as a proper desktop computer via Samsung’s DeX mode. It is the kind of build that makes you stare at your own peripheral collection with fresh suspicion.
Starting With a Smartphone, Not a Single-Board Computer
The project begins with a Samsung Galaxy S21 5G, and that choice matters. Most similar builds reach for a Raspberry Pi or another single-board computer as the computing core, but starting with a smartphone raises the stakes considerably. A phone brings its own battery management, wireless radios, camera hardware, and an entire mobile operating system, all in a package that, with its battery compartment removed, fits inside a once-wireless mouse with what the builder describes as shocking ease.
Critically, the Galaxy S21 5G supports Samsung DeX, the desktop mode that outputs a windowed, taskbar-style interface to an external display. That means the builder could leave the stock Android installation entirely untouched. There was no need to layer a Linux environment on top, and no need to replace the operating system with something like PostmarketOS, though both remain viable routes. DeX does the heavy lifting, turning the phone into something that genuinely behaves like a desktop PC the moment it is connected to a monitor.
According to Samsung Support, DeX compatibility extends across a wide family of devices: the Note 8 through to the Note 20 Ultra 5G, the S8 all the way through to the S25 series, the Galaxy Z Fold range, and various Tab models including the Tab S4 through Tab S9. The S21 sits comfortably within that supported list, which is precisely why it made such a sensible starting point for a build like this.
Galaxy S21 Inside Mouse: Thermal Management on a Budget
Fitting a smartphone into a mouse shell is one thing; keeping it from throttling itself into uselessness is another. A sealed plastic mouse body is not what thermal engineers dream about. The builder addresses this with brass, using it as a heat spreader inside the enclosure. It is a pragmatic solution: the Galaxy S21 5G’s own thermal management was never particularly elaborate to begin with, so a passive brass spreader is arguably not far behind what the phone enjoyed in its original form. In the video accompanying the build, the system appears to run without obvious thermal throttling, which is about as much as you can reasonably hope for in an enclosure that size.
The builder does acknowledge that liquid cooling would be the only real answer if throttling became a persistent concern, though fitting any kind of liquid loop inside a mouse body would be a considerable challenge beyond even this project.
What the S21 Brings Beyond DeX
It is worth noting what the Galaxy S21 series brought to the table when it launched. As Yahoo Finance reported at the time, the Galaxy S21 Ultra 5G was the first Galaxy device to let users run both a 120Hz refresh rate and a Quad HD+ display simultaneously, without having to choose between smoothness and resolution. While the standard S21 used here is not the Ultra variant, the broader S21 generation represented a meaningful step forward in Samsung’s hardware ambitions.
There was also the matter of the S Pen. CNBC noted that the S21 Ultra marked the first time a Galaxy S phone supported Samsung’s S Pen stylus, a feature previously exclusive to the Galaxy Note line. None of that is directly relevant to a phone sitting inside a mouse shell, of course, but it underlines that the S21 family was not a budget or throwaway choice of donor hardware.
The build is labelled a ‘PC inside a mouse’ by Gadget Industry, which is accurate in spirit if not in the strict IBM-compatible sense. ARM architecture, Android base, DeX desktop layer: it is a personal computer by any reasonable measure, just not one that would run your copy of WordPerfect 5.1.
