We don't enable Cairo at all for any users by default. It's hidden behind a pref, and that pref only works on Linux.
Bug 1642028 Comment 5 Edit History
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We don't enable Cairo at all for any users by default. It's hidden behind a pref, and that pref only works on Linux. It's either Direct2D, or if not available (due to platform or unsupported), then Skia is otherwise always the default.