No, you don't have to download everything. All games within our databases are browser-centered And do not need any download or installation. Having said that, some more mature games need Flash player, so You could have to set up it if you'd like to play A few of these games https://www.dmidcroms.com/CRS/Lists/DMIDCROMS%20Resources%20Feedback/DispForm.aspx?ID=45696