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Can Websites track my Theme?

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  • Last reply by Amelia

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Can websites i visit track my browsertheme for example system default or light or dark theme? I like the dark theme but i'm not using it because i fear it makes my browser much more unique, is that so? If so, is there a preference or another way to prefent websites from tracking my browser theme?

Can websites i visit track my browsertheme for example system default or light or dark theme? I like the dark theme but i'm not using it because i fear it makes my browser much more unique, is that so? If so, is there a preference or another way to prefent websites from tracking my browser theme?

Chosen solution

Yes, websites can see if you are using a dark or light theme via a css query, allowing javascript to find out and do something about it. For the nitty-gritty, look here https://developer.mozilla.org/en-US/docs/Web/CSS/@media/prefers-color-scheme

the browser.theme.content-theme preference can be used to change what Firefox does when it comes to this, note it affects settings and internal pages. It is an integer value with the following meanings:

0: Dark mode on everything (except private browsing, that disallows dark mode like that altogether, but can be changed by another preference) 1: Light mode on everything 2: Follow system theme (detect what the system theme is and use that) -- Default 3: Follow Firefox theme (what color the tab text is in -- if the text is bright (white) it would contrast on black, and therefore would mean you have a dark theme)

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Really? They can't? I think cor-el or jscher2000 told me they can, but then again how can i block that sort of spying? Any prefs?

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Chosen Solution

Yes, websites can see if you are using a dark or light theme via a css query, allowing javascript to find out and do something about it. For the nitty-gritty, look here https://developer.mozilla.org/en-US/docs/Web/CSS/@media/prefers-color-scheme

the browser.theme.content-theme preference can be used to change what Firefox does when it comes to this, note it affects settings and internal pages. It is an integer value with the following meanings:

0: Dark mode on everything (except private browsing, that disallows dark mode like that altogether, but can be changed by another preference) 1: Light mode on everything 2: Follow system theme (detect what the system theme is and use that) -- Default 3: Follow Firefox theme (what color the tab text is in -- if the text is bright (white) it would contrast on black, and therefore would mean you have a dark theme)