Apple has announced that Safari 10, out this fall, will block Flash by default, pretending it is not installed.
In a blog post, Ricky Mondello says that the goal is to improve security, performance, and battery life by forcing sites to use any available HTML5 implementations rather than Flash versions.
This works by lying to websites about what is actually installed on the computer. Mondello says:
By default, Safari no longer tells websites that common plug-ins are installed. It does this by not including information about Flash, Java, Silverlight, and QuickTime in
navigator.pluginsandnavigator.mimeTypes. This convinces websites with both plug-in and HTML5-based media implementations to use their HTML5 implementation.
The end result is that any site that has both HTML5 and Flash versions will end up using the HTML5 one because it thinks there is no Flash. If a site doesn't have an HTML5 version, the user will see the typical prompt asking them to install Flash. Safari will intercept this and let the user know they actually do have Flash installed and ask if they would like to enable it for the site.
The change is identical to a Chrome proposal that surfaced last month. Unlike the Chrome plan — which proposed to whitelist the top 10 sites — Safari will block legacy plug-ins on all websites.
For developers, one of the most common ways Flash is still used is in cutting/copying content from a web browser and the host OS clipboard. One alternative to the Flash plug-in method is the the Clipboard.js JavaScript library which uses execCommand to pull content from the browser. Currently, this is supported in all browsers except Safari, but once Safari 10 is released, it will work everywhere.
Blocked plug-ins will first appear in Safari 10, which is part of the new macOS Sierra release, due out in the fall. Developers registered in the Apple Developer Program can install a beta of macOS Sierra now. A public beta will launch in July.