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Plugins and Page Info menu: "Block" doesn't do the same thing as "Never Activate"?

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  • Last reply by user885311

user885311
user885311
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I notice that when I set one of my browser plugins (say, Flash Player) to "Never Activate", then websites behave as if the plugin isn't installed on my computer at all; it does not detect the plugin's presence.

However, if I set Firefox to "Block" a plugin on a specific site using the "View Page Info" menu, then the website can still detect that the plugin is installed, and it will serve content associated with that plugin (say, a Flash-based video player), but Firefox will simply replace the content with a message box saying "This plugin is blocked".

This seems like inconsistent behavior to me (shouldn't "Block" do the same thing as "Never Activate"?), so I'd like to know if there is a way to set a plugin to never be activated or detected on a per-site basis.

I notice that when I set one of my browser plugins (say, Flash Player) to "Never Activate", then websites behave as if the plugin isn't installed on my computer at all; it does not detect the plugin's presence. However, if I set Firefox to "Block" a plugin on a specific site using the "View Page Info" menu, then the website can still detect that the plugin is installed, and it will serve content associated with that plugin (say, a Flash-based video player), but Firefox will simply replace the content with a message box saying "This plugin is blocked". This seems like inconsistent behavior to me (shouldn't "Block" do the same thing as "Never Activate"?), so I'd like to know if there is a way to set a plugin to never be activated or detected on a per-site basis.

All Replies (2)

cor-el
cor-el
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  • Top 10 Contributor
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With "Never Activate" you completely disable the plugin and the plugin is never used and websites can't detect it via navigators.plugins or otherwise via JavaScript. With "Ask to Activate" you allow to be prompted to use the plugin and you can set an allow exception to avoid this prompt on trusted websites. With "Always Activate" you allow the plugin to run all the time unless you block it via the permissions because you want to be prompted. If you block the plugin via the permissions then this will only prevent the plugin from getting activated without confirming this and website are still able to detect the plugin because otherwise they could/would fallback other ways to play the media file like an HTML5 media player.

user885311
user885311 Question owner
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That's kinda of my point, you see; I actually want to force the site to use its fallback method, but I still want to be able to use the plugin on other sites. The fact that Firefox doesn't allow for this is just odd to me.