Newgrounds are developing an open-source, browser-based Flash emulator called Ruffle, which will enable people to play old-Flash games and view content created with the tool.
Tom Fulp, founder of Newsgrounds says:
Flash was created by FutureWave, and originally known as FutureSplash Animator. FutureWave was acquired by Macromedia (creators of web publishing software, Dreamweaver) in 1996 and renamed the product Flash. Adobe acquired Macromedia in 2005, by which point the tool had become popular for creating games that could be played in the browser.
This included many retro-games and there were lots of official and unofficial ports of games such as Pong, Tetris, Pac-Man, Metal Slug and Super Mario World.
However, a combination of the iPhone’s lack of Flash support and the notorious security issues with the product meant that the popularity began to fall, leading to Adobe announcing the end of life for Flash to be in 2020.
Ruffle is in earlier stages at the moment, but you can see a demo here and the source code on Git Hub here.