--- /dev/null
+# at-rule-no-unknown
+
+Disallow unknown at-rules.
+
+```css
+ @unknown (max-width: 960px) {}
+/** ↑
+ * At-rules like this */
+```
+
+This rule considers at-rules defined in the CSS Specifications, up to and including Editor's Drafts, to be known.
+
+## Options
+
+### `true`
+
+The following patterns are considered violations:
+
+```css
+@unknown {}
+```
+
+The following patterns are *not* considered violations:
+
+```css
+@charset "UTF-8";
+```
+
+```css
+@CHARSET "UTF-8";
+```
+
+```css
+@media (max-width: 960px) {}
+```
+
+```css
+@font-feature-values Font One {
+ @styleset {}
+}
+```
+
+## Optional secondary options
+
+### `ignoreAtRules: ["/regex/", "string"]`
+
+Given:
+
+```js
+["/^my-/", "custom"]
+```
+
+The following patterns are *not* considered violations:
+
+```css
+@my-at-rule "x.css";
+```
+
+```css
+@my-other-at-rule {}
+```
+
+```css
+@custom {}
+```