Firefox will be Blocking Invisible Flash Content from August 2016

Firefox has announced that it will be blocking invisible Flash content from August 2016.  The move has been prompted by the risk that Flash content poses to Firefox users. The update will also help to reduce Firefox browser crashes and should improve battery life on laptop computers.

Blocking Invisible Flash Content Will Improve the User Experience

Flash has been depreciating for some time, as web developers switch to alternative methods of displaying online video content. Many websites now use HTML5 to show video content, which is something Firefox wants to encourage. Firefox reports that its browser has been crashing much less frequently as web developers have switched to HTML5 from Flash player. There was a sharp fall in the Firefox crash rate following YouTube’s decision to switch to HTML5 and the fall has continued as Facebook switched to HTML5 video.

The decision to block invisible Flash content is a no brainer. Hidden Flash files are used on malicious websites for nefarious purposes. Hidden Flash files are often involved in drive-by downloads of malware and ransomware. Hidden Flash scripts are also used to spy on website visitors. Blocking invisible Flash content should improve the user experience. Firefox expects the crash rate to fall by 10% as a result of the move.

Firefox will be blocking Flash content that is not essential to the user experience. Firefox’s Benjamin Smedberg said in a recent blog post “Plugins often introduce stability, performance, and security issues for browsers. This is not a trade-off users should have to accept.”

Firefox will continue to support legacy Flash content, although not for much longer. From March 2017, it will be necessary for Flash content to be manually activated in the browser. In 2018, Flash support is expected to be dropped entirely.

The End of Flash is Nigh

Firefox also announced that later this year the browser will block the use of Flash to check content viewability, which is something that is commonly used to measure advertising. The function will be replaced with an HTML Intersection Observer API.

The move by Firefox has come a little later than other browser developers. Google, Microsoft and Apple have already started to limit Flash content. The Safari browser has blocked certain Flash since 2013, Chrome limited Flash since September 2015, and Microsoft will be limiting Flash in its Edge browser from August 2, 2016.

Author: Richard Anderson

Richard Anderson is the Editor-in-Chief of