emulationonline

I networked a 6502 a while ago in order to capture some behavior that isn't well documented.

You can interact with it using a wasm-based assembler in your browser. Programs only get 100 cycles to run but that should be plenty if you just want to poke around.

https://chiplab.emulationonline.com/6502/

I built something like a simpler version of this for testing some edge cases of the 6502. You can play with it through a browser here: https://chiplab.emulationonline.com/6502/