This is the first known instance of bsnes running in a web browser. Unlike snes9x, it is a cycle accurate emulator and capable of certain graphical effects that snes9x (and most other emulators) don't emulate.
It is currently extremely slow. This is an emulator (SNES, 65C816 interpreter and other chips) running inside of an emulator (RISC-V interpreter) running inside of an emulator (WebAssembly black box).
Proposed improvements to the RISC-V portion (the code that I own) include exploring static or dynamic recompilation, by way of either generating WebAssembly directly or leveraging a C compiler.