There are a lot of technologies that can be used for chat. Literally by looking for a flash chat room (searched "flash chat room for a website") the third result I got in google was a html5 based one. Just to name a few random examples of open source html/css/js based chats: https://github.com/credija/opa https://conversejs.org/ https://rocket.chat/ https://firechat.firebaseapp.com/ https://deadsimplechat.com/ and since I mentioned css, I have to add this: https://github.com/kkuchta/css-only-chat :)