Fonts

defineFont is a framework-agnostic way to register fonts inside Salty CSS. It writes the @font-face rules into your build output, exposes the font as a CSS custom property, and returns a small object that can be used as a class, a CSS variable, or an inline style.

It's the right tool when you want fonts to live alongside the rest of your design tokens — same *.css.ts files, same build pipeline, no extra plugin.

Already using next/font? That's fine. next/font integrates with Next.js's build optimisations (subsetting, automatic preload) and Salty CSS happily reads the CSS variable it exposes (var(--font-family-…)). Use defineFont when you want a single registration path that works the same way across React, Vite, and Astro, or when you need finer control over the generated @font-face.

Local font files

Pass a variants array. Each variant has its own src, optional weight, style, and the usual @font-face descriptors:

// /styles/fonts.css.ts
import { defineFont } from "@salty-css/core/factories";

export const inter = defineFont({
  name: "Inter",
  fallback: "system-ui, sans-serif",
  display: "swap",
  variants: [
    {
      src: "/fonts/Inter-Regular.woff2",
      weight: 400,
      style: "normal",
    },
    {
      src: "/fonts/Inter-Italic.woff2",
      weight: 400,
      style: "italic",
    },
    {
      src: "/fonts/Inter-Bold.woff2",
      weight: 700,
      style: "normal",
    },
  ],
});

A few things to know:

• src accepts a string URL, a { url, format, tech? } object, or an array mixing the two. When you pass a string, Salty CSS detects the format() from the file extension (woff2, woff, ttf, otf, eot, svg, ttc).
• Paths starting with / resolve against your app's public asset root; relative paths (./fonts/Inter.woff2) resolve against the location of the rule emitted in your build output. Pick one convention and stick with it.
• display defaults to 'swap' if you don't set it per-variant and don't set it on the parent.
• The fallback string is appended to the generated font-family value, so you get FOUT-safe rendering for free.

Remote stylesheets (Google Fonts, etc.)

Use import instead of variants when the font is hosted somewhere that already provides a @font-face stylesheet:

// /styles/fonts.css.ts
import { defineFont } from "@salty-css/core/factories";

export const outfit = defineFont({
  name: "Outfit",
  fallback: "system-ui, sans-serif",
  import: "https://fonts.googleapis.com/css2?family=Outfit:wght@300;400;600&display=swap",
});

Salty CSS emits an @import url(...) at the top of the stylesheet (above any @layer) so the remote rules load correctly.

variants and import are mutually exclusive — pass one or the other, not both.

Using the returned value

Calling defineFont(...) returns an object with four members. Use whichever fits the situation:

It also stringifies to .fontFamily, so you can drop the object straight into a style object:

import { styled } from "@salty-css/astro/styled";
import { inter } from "../styles/fonts.css";

export const Heading = styled("h1", {
  base: {
    fontFamily: inter, // → "Inter, system-ui, sans-serif"
    fontWeight: 700,
  },
});

Read the variable when you want themed overrides:

import { styled } from "@salty-css/astro/styled";
import { inter } from "../styles/fonts.css";

export const Body = styled("p", {
  base: {
    fontFamily: `var(${inter.variable})`,
  },
});

Apply the class when you want to scope the font to a subtree without touching individual components:

---
// src/pages/index.astro
import { inter } from "../styles/fonts.css";
---

<main class={inter.className}><slot /></main>

A pragmatic font-family token

Pair defineFont with defineVariables so call sites reference a token, not a specific font import:

// /styles/fonts.css.ts
import { defineFont } from "@salty-css/core/factories";
import { defineVariables } from "@salty-css/core/factories";

export const inter = defineFont({
  name: "Inter",
  fallback: "system-ui, sans-serif",
  variants: [{ src: "/fonts/Inter-Regular.woff2", weight: 400 }],
});

export default defineVariables({
  fontFamily: {
    body: inter.fontFamily,
    heading: inter.fontFamily,
  },
});

styled("p", { base: { fontFamily: "{fontFamily.body}" } });

Swap fonts later by changing the variable definition — every call site updates.

Configuration reference

The full option shape (see define-font.ts for the type):

Variant shape

FontSrc is { url: string; format?: FontFormat; tech?: string }.

See also

• Variables — use defineFont output as a token.
• Templates — bundle font + weight + line-height into reusable text styles.
• Imports — use defineImport for stylesheet-level imports that aren't font-specific.