Here's an overview on different web technologies supported by browsers and available for game developers today:
HTML5 (WebGL) technology
Supported by almost all browsers today, and without requiring any plug-ins to install, we recommend HTML5 (WebGL) technology for developers to get started with today. We have a list of HTML5 engines, Cross-Platform Engines, Toolkits and Libraries, or the Facebook-Unity WebGL option.
On another note, Facebook Gameroom has built-in support for Web Games built in Flash, working independently from the browser announcements listed on this page. Players will be able to continue playing their games in Facebook Gameroom.
Adobe announced its plans to stop updating and distributing Flash Player at the end of 2020. While games built in Flash will run on Facebook until the end of 2020, we strongly advise developers to follow the timelines set by browsers, as this may impact your decision to migrate sooner.For developers building new games, we strongly recommend using open web standards. To learn more about how you can migrate off Flash, you can sign up for our upcoming webinar or visit our blog post.