This is using my gameboy emulator, binjgb[0], on the website! (well one of my gameboy emulators, heh [1][2]) It's been used as the emulator for GB Studio for a little while now, but I don't know how often people embed it in their websites, so it's really cool to see.
[0] https://github.com/binji/binjgb [1] https://github.com/binji/pokegb [2] https://binji.github.io/raw-wasm/badgb/