Google will stop supporting Flash later this year, which includes web pages with Flash content as well as SWF files.
If an HTML page contains Flash content it will still be indexed, but Google will ignore the Flash components. If a page is built entirely with Flash (SWF files) then it will not be indexed at all.
With that being said, it’s still not advisable to have web pages with Flash content as it’s disabled by default in today’s web browsers. Although Google is technically capable of indexing web pages with Flash, it won’t do any favors for your search rankings given that it’s not mobile-friendly.
At one time, when HTML was limited, Flash was a used as a way to add some life to web pages. Site owners were able to add rich animations, media, and other interactive elements. At it’s peak, Flash hit 500 million downloads in the second half of 2013 alone.
Now that HTML5 is more capable it can be used as an alternative to Flash. JavaScript is also an acceptable alternative, though Google often recommends avoiding it as much as possible.
Google pays homage to the history of Flash in its announcement:
“Flash was the answer to the boring static web, with rich animations, media, and actions. It was a prolific technology that inspired many new content creators on the web. It was everywhere. The Flash runtime, which plays Flash content, was installed 500 million times in the second half of 2013.”
Google estimates that most users and websites will not see any impact from this change.