Mozilla has been working on the feature for a while now
Firefox 17 is now in beta and with it is a very cool feature, click-to-play plugins. This enables users to disable all browser plugins and only run them on demand, for the content they want. What this means is no more annoying Flash ads, no more Java applets loading without you knowing about it and so on.It's a great feature for security, usability and performance, as not having to load a ton of Flash content frees up resources for the stuff you actually want to see.
The feature has been in testing in Firefox for a while, but it is now activated by default in Firefox 17 for older plugins. It's still not enabled by default for all plugins, i.e. it's not set to "on" from the get go, just the ones that are outdated.
"Firefox 17, coming out today on Beta, introduces a new solution for dealing with vulnerable or outdated plugins. Plugins that are blocked with the click-to-play flag will not load by default, but can be easily activated by users," Mozilla's Jorge Villalobos wrote.
"This gives us a more user-friendly way to warn about plugins that should be updated, that give users better control over their browsing experience," he said.
The advantages of click-to-play are obvious, though for now Mozilla is focusing on security. There are no controls for the feature, it will be enabled by default for old plugins, i.e. you'll have to "click" on the content to load the plugins.
"The large scale plugin update notification we deployed last week used the old update notification mechanism for Firefox 16 and below, and the new click-to-play mechanism for Firefox 17 and above," Villalobos explained.
Mozilla is still working on implementing the controls, which would allow you to block all plugins by default and then pick where you want them to run.
However, if you're comfortable, you can go to about:config search for plugins.click_to_play and set it to "Enabled." This will block all plugins all the time.