Flash games or Browser games can be run using standard web technologies or browser plug-ins. The creation of such games usually involves use of standard web technologies as a frontend and other technologies to provide a backend. Browser games include all video game genres and can be single-player or multiplayer. Browser games are also portable and can be played on multiple different devices, web browsers, and operating systems. 
Browser games come in many genres and themes that appeal to both regular and casual players. Multiple browser games have developed beyond the online platform to become large titles or franchises sold physically in stores, in online marketplaces like Steam or XBLA, or in decentralized distribution platforms such as itch.io. Some of those titles are Alien Hominid, Bejeweled, Bloons, Club Penguin, Cookie Clicker, Meat Boy, and Transformice.
The old gaming sites of Y8, Friv, Kizi, Agame … in flash form are no longer used today due to the improvement of computer and smartphone browsers. Today, to play these games, you can find game websites in html5 format.
And Friv, Y8, Agame
… they also used this game platform.