Firefox to start blocking Flash content in August – Ars Technica

Firefox will begin retiring Adobe Flash on August 2 with the release of Firefox 48. In 2017, probably with Firefox 53, Flash plug-ins will require the user to actively click-to-play.

In Firefox 48, Mozilla will enable a new Firefox plug-in blocklist by default. Initially the blocklist will be small, mostly containing URLs of Flash SWF files that have been identified by Mozilla as supercookies (i.e. cookies that are very hard to shake off) or fingerprinting files (i.e. they scan your system and create a unique fingerprint, again usually for tracking purposes).

The Github repo explains the criteria for adding new SWFs to the blocklist:

  • Blocking the content will not be noticeable to the Firefox user
  • It is possible to reimplement the basic functionality of the content in HTML without Flash
A graph, produced by Mozilla, showing plug-in crash rate in Firefox over time. The drop when YouTube switched to HTML5 is all you need to know.

The Mozilla blog post introducing this blocklist only mentions supercookies and fingerprinting files in passing, though. Rather, Mozilla explains this move as the beginning of the end for Flash: “… Plug-ins often introduce stability, performance, and security issues for browsers. This is not a trade-off users should have to accept.” Thus, Mozilla will gradually add Flash elements that are “invisible to users” to the blocklist, which is “expected to reduce Flash crashes and hangs by up to 10 percent.”

Then, in 2017 (probably Firefox 53 in May), Flash content will be entirely click-to-play: so, you’ll still be able to play Flash games and watch Flash videos, but all of those Flash ads and hidden Flash elements will be completely blocked. (This is functionally very similar to how Chrome has handled Flash elements since September 2015.)


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