require-src-in-font-face

Require a src descriptor in every @font-face declaration block.

Rule catalog ID: R022

Targeted pattern scope

Every @font-face block in the stylesheet.

What this rule reports

@font-face blocks that are missing a src descriptor entirely.

Why this rule exists

The src descriptor is the only mechanism by which a browser locates and downloads a custom font file. An @font-face block without src is silently inert: the browser parses it without error but the family name can never resolve to an actual typeface. In practice this is always a typo or incomplete migration.

Unlike most missing-descriptor rules this failure is absolute: there is no fallback behavior, no default value, and no workaround. The block has zero effect until src is added.

❌ Incorrect

/* src omitted entirely — @font-face block has no effect */
@font-face {
  font-family: "Inter";
  font-weight: 400;
  font-style: normal;
  font-display: swap;
}

✅ Correct

@font-face {
  font-family: "Inter";
  font-weight: 400;
  font-style: normal;
  font-display: swap;
  src: url("./inter-regular.woff2") format("woff2");
}

When not to use it

If you use a CSS pre-processor or build tool that programmatically injects src into @font-face blocks after a partial declaration, you may see false positives during static analysis. In that case, disable this rule for the affected source files.

Targeted pattern scope​

What this rule reports​

Why this rule exists​

❌ Incorrect​

✅ Correct​

When not to use it​

Further reading​