The Flash authoring tool comes bundled with a standalone Flash movie player that can open .swf files. It's available here, but I have no idea if this will continue to work (the page warns against using this if you're not a developer): https://www.adobe.com/support/flashplayer/debug_downloads.ht...

It's also possible to export any Flash movie as a standalone executable with the Flash runtime baked in. This should be immune to any sort of deprecation. Of course this relies on the developer who holds the original source file to do the exporting.

There's also a tool for converting flash to html5, but i'm not sure this would work 100% for games.

That standalone executable will only run on the operating system it's been exported for.

From the article:

"Game developers that formerly built games for Flash are quickly switching to HTML and seeing great results. Last week, Kongregate published​ data about the transition to HTML and the trends in game technologies used on their web gaming platform."

So it looks like stuff is being converted over from flash

Current and recent games. The poster is replying to games that haven't been in touched in 10+ years. Classic web games.