TL;DR: Swiffy will stop converting SWF files from 1st July, 2016.

Recently, we announced that we're transitioning all of our display ads to HTML5. As part of this transition, we're sunsetting our Swiffy Flash conversion service and support for the Swiffy Flash extension on July 1st 2016. After this date, you will no longer be able to use either to convert SWF files to HTML5. We will continue to serve the Swiffy runtimes, so any file you convert before the sunset date will continue to play.

Today more consumers are using the web in HTML5-compatible environments than Flash-compatible environments. In order to reach as large an audience as possible, we encourage everyone to transition to HTML5 authoring.

Developers who currently create Flash SWF files have several ways to switch to HTML5, including Adobe Animate and Google Web Designer. If you need to play an existing Flash SWF file in your browser alone, you may be able to use Mozilla's Shumway.