The problem I ran into with this is when using Apple’s SF fonts. Some of the weights transfer to the phone, some don’t (mainly I have problems with SF UI Display Thin and some other more obscure weights).

Maybe it has to with some conflicts with the system version of San Francisco on the connected iPhone?

yes, next update will include a verbose listing of fonts that failed to load and a reason why. Truetype fonts (.ttf) always work in my experience. Postscript type 1 fonts always fail. OpenType fonts (.otf) can contain postscript type 1 glyphs or true type. If you have the choice, always select the true type font.

Hey Chris, Thanks for your information and advice. Am I right in saying that there is a much better chance that fonts would render on the app if they were Truetype? (I'm assuming being present on the system is a given here btw).

It would be great in the future - when the name of the font would be listed - if the reason why the font is not loading would also be listed btw.

In addition to the font licensing issue Elaine mentions, there are a few other reasons why a font might fail to transfer from desktop to device:
1) its not actually present on your Mac. XD will silently fallback to a system font without telling you. iOS/Android will warn on any missing font. The fallback system font is different on desktop than on device. Use FontBook app to verify that a font in the document is installed on your machine.

2) its not a compatible font format for this device. Postscript type 1 fonts are in this category. .otf fonts can sometimes contain postscript format fonts (as in the FontAwesome case).

3) its just too darn big (over 50 MB). Memory is limited on mobile devices (typically 1 GB for everything running on the device, including OS). Mobile operating systems will kill your process if its trying to use up too much memory. It would be unwise to design content for mobile that uses fonts > 50MB in size. That said, its pretty rare for fonts to get this big.

In an upcoming update to the iOS app, the font warning dialog will list the name of each missing font, along with the reason it is missing. This should help identify what you can do to address the issue.

Mike, FontAwesome works if you install the .ttf (true type font) variant. The .otf variant is in the older Postscript type 1 format, which is not supported on iOS. Use FontBook to disable/remove your current variant on your Mac, then download FontAwesome.zip again, unzip, and look in the "fonts" directory. Install the fontawesome-webfont.ttf file.

I use font awesome almost exclusively for my icons in apps. In the new device preview, that font will not render and i get the question mark image. I need these to remain editable in the future so I don't want to convert to paths. Any other options or chances of brining that font in the future? Without font awesome support (it works when sharing the a link to the project), the new XD app will unfortunately not be useful for my workflow at all.

Hey Elaine, Thanks for your feedback. I am trying to use LT Avant Garde Gothic. Converting them as paths is not good as I need them editable. Can you tell me more about the Postscript aspect or point me to more information as I may be able to convert them to Opentype or Truetype. Are you saying they might work if I were to do that? They embed fine in PDFs from Illustrator. Any further thoughts?

Also, as they won't ever be finally delivered via the companion app should lisencing restrictions really get in the way?

What value is it displaying my design work on the xd mobile companion app without fonts? What can I do or will you be doing about this?