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Is there a Firefox extension that prevents websites from detecting what operating system you're using?

Also, if there isn't a plugin, is it possible to write one?

I know I can disable websites from seeing my OS type by disabling JavaScript, but can I just disable just the feature that detects the OS?

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Disabling JavaScript does not prevent browser/OS detection, just deactivate it and see for yourself. Having it enabled might provide some information that the method described below hides though.

Use this addon to change your reported user agent (i.e. browser), which includes information about your OS.

Open the options, create a New... user agent like the one shown below, and select it from a submenu of the Tools menu.

enter image description here

enter image description here

enter image description here

This user agent description provides no information at all about your browser or operating system (except what could be gathered using other methods, like JavaScript-based detection), which might interfere with some browser-switches on web sites. Remove the information you don't want to provide the web sites and leave the rest in.

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Also, it might be possible to get some information about your browser via CSS. I'd need to confirm that though, as I'm not that into web development. – Daniel Beck Jun 10 '11 at 9:03
@Daniel; CSS is clientside, entirely, while different styles may render differently in different browsers, there is no way to send that information back to the server. – Phoshi Jun 11 '11 at 21:11
@Phoshi Yes, you can actually use CSS browser switching and e.g. background-image: url(onlyLoadedInMozillaOrSo.png) for some elements that are visible/loaded or not, depending on browser-specific CSS handling (like IE's * html #element, IIRC). It's tedious, but can be done. It might actually be the most reliable solution: While the user agent can be faked or cleaned by proxies, and JavaScript is (was?) commonly deactivated, nobody in their right mind deactivates CSS or emulates the behavioral quirks of another browser. – Daniel Beck Jun 11 '11 at 21:23
@Daniel Back; ooh, I stand corrected, I hadn't considered that angle at all. It'd be really fiddly, but that could end up working quite effectively. – Phoshi Jun 11 '11 at 22:17
@Phoshi You could, of course, go the email route and disable loading of images, but that would really diminish the usability of most web sites, I believe. It'd be interesting so see if there's a way to circumvent this also, but as I said, I'm not that much of an expert in web development... – Daniel Beck Jun 12 '11 at 13:09

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