You can check in Font Book for font issues like corrupted and duplicate fonts.

You can right-click and select "Inspect" to open the built-in Inspector with this element selected.

• https://developer.mozilla.org/en-US/docs/Tools/Page_Inspector/How_to/Examine_and_edit_HTML

You can check in the Rules tab in the right panel in the Inspector what font-family is used for selected text. You can check in the Fonts tab in the right panel in the Inspector what font is actually used because Firefox might be using a different font than specified by the website.

• https://developer.mozilla.org/en-US/docs/Tools/Page_Inspector/How_to/Edit_fonts

Thank you for your quick reply, cor-el!

I checked and the website uses Helvetica. I reset the Font Book, but the problem still continues. If I take the code: <span style="font-family: Helvetica, Arial, sans-serif; font-size: 14px;">text</span>

And change it to: <span style="font-family: Arial, sans-serif; font-size: 14px;">text</span>.

Everything works fine!

But how do I do this on a high level? Also, if I keep Helvetica and turn on Italic on the Fonts tab, everything works fine as well.

Have the same issue. Going into the inspector and literally changing the font used (which, obviously, will reset back when you refresh the page) is clearly not a global solution.

For me, this problem affects, not Helvetica, but Times New Roman. I find this happens on multiple different websites, and believe it started for me when I updated to MacOS Ventura.

You may have another (third-party) font that identifies itself as "Times New Roman" and that can't be accessed by Firefox due to sandbox restrictions.

Is there a way to confirm and remedy this? I checked the Font Book on Mac and I only have one Times New Roman installed (according to the app). I cant uninstall the existing Times New Roman font since it is a "system font"