What does the message "Request for font "Noto Sans" blocked at visibility level 1 (requires 3) - node.js" implies and how to prevent it?

Question

My website always displays this warning in the console :

"Request for font "Noto Sans" blocked at visibility level 1 (requires 3) - node.js"

Noto Sans is not loaded as a file by the website, it is only used as a backup font if other fonts do not display. Yet it is the only backup font where I get this warning.

What does this message mean and how to eventually prevent it ?

This is the full code of the page were the problem figures:

<style>
.addFont {
  font-family: 'ui-sans-serif', 'system-ui', '-apple-system', 'BlinkMacSystemFont', 'Segoe UI',
    'Roboto', 'Helvetica Neue', 'Arial', 'Noto Sans', 'sans-serif', 'Apple Color Emoji',
    'Segoe UI Emoji', 'Segoe UI Symbol', 'Noto Color Emoji';
}
</style>

<span class="addFont">Text</span>

Note: these fonts & fallback fonts are initially from the TailwindCSS default "font-sans" class.

What browser are you using? Firefox has this kind of visibility levels implemented to prevent user installed fonts from loading from the local system, to reduce the possibility of fingerprinting by installed fonts. — Christopher
– Christopher, Commented Apr 10, 2023 at 18:16

Eli O. · Accepted Answer · 2023-04-10 18:26:54Z

3

Simply removing the 'Noto Sans' and 'Noto Color Emoji' fallback fonts (in my case in TailwindCSS "font-sans") solved the problem.

It seems that the font was blocked by Firefox for preventing fingerprinting by installed fonts, as pointed out by @Christopher in comments.

answered Apr 10, 2023 at 18:26

Eli O.

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1 Comment

Christopher Over a year ago

If you provide the font from the server (for example: @font-face { font-family: 'Noto Color Emoji'; src: url('/path/to/NotoColorEmoji.ttf') format('truetype'); }), it wouldn't be blocked on the page by the privacy protection tools firefox has recently implemented.

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