How to identify illegal operators, anyone knows?

It's hard to recognize them quickly, but I'm guided by the image of the casino and the games, there are some that leave a lot to be desired

Hello Slotprovider.

If you mean the game providers, then mostly you can recognize fake ones by inspecting from which website is the game loaded.

If you are talking about casinos illegally operating on a regulated market, you can check the casino license in the footer of the website. Or check the list of licensed casinos for certain country - usually you can find them on regulator's website.