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Citra
Citra is a Nintendo 3DS emulator from the same team behind the trailblazing yuzu Switch emulator (see above). The big difference is that 3DS has a far more modest hardware specification, because it's considerably older. It also helps that this emulator has been in development for a considerable time. As a result, Citra is relatively mature. This can be seen with the setup wizard that helps you choose between versions and automatically download the binaries of whatever you choose. It also means you can play real games if you have the hardware facility and permission to copy them from your cartridges. The main Qt-based UI window is almost identical to yuzu, and it's obvious that both emulators and hardware have a lot in common. But the big difference is that, with Citra, you can actually play games. Like the Wine compatibility list for Windows titles, the wiki contains a list of games and a rating of how well they work: 36 titles are rated as having "Perfect" emulation, and a whopping 62 reportedly work "Great."
The games themselves will need to be sourced before you can play anything. Using your own cartridges is likely the most legal option. Games are also encrypted against your original hardware, which can create more legal and moral hurdles, but Citra is capable of excellent performance if you get that far. Like many emulators, modules are used to perform the CPU, system, input graphics, and audio hardware. Each of these can be configured separately and changed to adjust performance for your specific system. In particular, you can change the rendering's native resolution so that the output supersedes the original viewport's size. The original 3DS selling point, of course, was its 3D screen. Unfortunately, this isn't yet supported, even if you have the hardware, but touch is emulated, as is network gameplay, so you get almost the whole experience.
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