In a nutshell the answer is no, you do not need to download anything whatsoever in order to enjoy Big Time Gaming titles.
This means you will not have to download an online casino’s software in order to play, as was common in yesteryears. Nor will you have to download any of the individual games. Rather, both the casino and the actual BTG games are all exclusively available in the instant play format, which you access directly from your web browser.