I think that Firefox should be able to display flag emoji on Windows and may use the Segoe UI Emoji font.

• about:config => font.name-list.emoji = WIN: "Segoe UI Emoji, Twemoji Mozilla"

Twemoji Mozilla is a font that comes with Firefox that can be used as fallback.

You can check in the Inspector what font is being used.

• https://unicode.org/emoji/charts/full-emoji-list.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 Font 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

Hi Hans, I run Windows 10 and I see that issue on the list here:

https://emojipedia.org/flags/

The page specifies each "letter" of the country code separately, and I guess the browser is responsible for combining them?

After searching around for a while, it seems the Windows Segoe UI Emoji font does not support country flags for reasons that don't seem to be well explained. If yours was working for a while, it is possible that an add-on was detecting and substituting them somehow?

You can try to edit font.name-list.emoji and remove the first part leaving only "Twemoji Mozilla" (without quotes).

• font.name-list.emoji = "Twemoji Mozilla"

Hmm, that didn't make any difference for me in a quick try. Perhaps there is some preference for the OS font that lurks elsewhere.

You can try to set gfx.bundled-fonts.activate = 1

Note that you need to close and restart Firefox to apply the change (pref is read at startup).

0     disable use of app-bundled fonts
> 0   enable use of app-bundled fonts
< 0   default (auto): decide at startup, based on the system environment

Success! That change --

double-click gfx.bundled-fonts.activate and edit the value from -1 to 1

-- and then restarting Firefox, allows the flags to display.

Thanks for your answers and suggestions! Modifying the setting "gfx.bundled-fonts.activate" from -1 to 1 on "about:config" did show flag emojis again on the page:

https://emojipedia.org/flags/

On my own web application they still did not show:

https://reiseberichte.reisen/themen/reiseberichte/reiseberichte.htm

By test however, I managed to show them on that page, if I explicitely add "Twemoji Mozilla" to the CSS style "font-family" for the corresponding tag.

I also have a YouTube channel, where I use flag emojis in video title/description. There, they are not shown as well. Obviously YouTube does not have "Twemoji Mozilla" contained in his styles, whereas "Emojipedia" does.

So, I conclude, Firefox on Windows does (currently) only show flag emojis, if the font "Twemoji Mozilla" is applied and if "gfx.bundled-fonts.activate" is set to 1. These two conditions were not necessary (at least not by explicite configuration) for Firefox on Windows during some months ago. Unfortunately not satisfactory these flag emoji issues on Windows (for Firefox and Chrome as well)...

Thanks for your suggestions! Modifying setting "gfx.bundled-fonts.activate" from -1 to 1 on "about:config" did show flag emojis again on the page:

https://emojipedia.org/flags/

On my own web application they still did not show. By test however, I managed to show them on that page, if I explicitely add "Twemoji Mozilla" to the CSS style "font-family" for the corresponding tag.

I also have a YouTube channel, where I use flag emojis in video title/description. There, they are not shown as well. Obviously YouTube does not have "Twemoji Mozilla" contained in his styles, whereas "Emojipedia" does.

So, I conclude, Firefox on Windows does (currently) only show flag emojis, if the font "Twemoji Mozilla" is applied and if "gfx.bundled-fonts.activate" is set to 1. These two conditions were not necessary (at least not by explicite configuration) for Firefox on Windows during some months ago. Unfortunately not satisfactory these flag emoji issues on Windows (for Firefox and Chrome as well)...

You will probably have to wait for Microsoft to update their Segoe UI Emoji font and add the flag symbols. In Firefox you can probably fix this with code in userContent.css.