| KEGS | Full-featured Apple IIGS emulator (Kent's Emulated GS) originating in the 1990s. | downloadable |
| Kega Fusion | Steve Snake's all-in-one freeware emulator covering the full Sega 8-bit and 16-bit console line. | downloadable |
| Kenbak-1 | From-scratch browser emulator of the Kenbak-1 (1971), widely credited as the first commercial personal computer: a machine built from TTL logic with no microprocessor, 256 bytes of memory and a front panel of lamps and buttons, with a full debugger. | online |
| KiGB | Portable and accurate Game Boy, Game Boy Color and Super Game Boy emulator. | downloadable |
| Klive IDE | Electron-based emulator and development environment for Sinclair machines written in TypeScript and WebAssembly. | downloadable |
| Kronos | Actively developed Sega Saturn and ST-V emulator forked from the Yabause lineage. | downloadable |
| Kung-Fu Master | Irem's 1984 Kung-Fu Master arcade machine, running in the browser with an in-frame Zilog Z80 debugger. | online |