Fonts on a Delta site are installed, not linked. Delta → Fonts holds every family the site can use, and the files sit on your own server.
Two ways in
Pick a family from the Google catalogue and Delta downloads it, so the visitor’s browser never calls Google. That keeps the site self-contained and avoids sending your client’s visitors to a third party, which matters if anyone has asked you about GDPR.
Or upload the files for a licensed family. woff2, woff, ttf and otf are accepted; woff2 is the one to use if you have it.
“Install Inter for body text and Fraunces for headings.”
“Here are the client’s licensed font files. Install them and use them for headings.”
Pick the weights you need
A family can be installed at chosen weights rather than all of them. Every weight is another file the visitor downloads, so install the two or three the design actually uses.
Then point a slot at it
Installing a font does not change the site. Four slots decide where it is used: text for running copy, title for headings, display for a hero, mono for code. Ask for the family in a slot and the site picks it up:
“Use Fraunces for the title slot.”
Linking a font is refused
A stylesheet cannot pull a font from a CDN. @import is stripped when styles are written, so the usual @import url(fonts.googleapis.com…) will not survive, and neither will a hand-added link to a font host.
This is deliberate. A CDN font is a request you do not control, on every page load, forever. Install the family instead. It is the same font, served from your own domain.
For developers
Files live under uploads/21press-delta/fonts. Installing writes the @font-face set; the slots are the --font-* tokens, set through the tokens rather than in CSS.