--- /dev/null
+# unit-no-unknown
+
+Disallow unknown units.
+
+```css
+a { width: 100pixels; }
+/** ↑
+ * These units */
+```
+
+This rule considers units defined in the CSS Specifications, up to and including Editor's Drafts, to be known.
+
+## Options
+
+### `true`
+
+The following patterns are considered violations:
+
+```css
+a {
+ width: 10pixels;
+}
+```
+
+```css
+a {
+ width: calc(10px + 10pixels);
+}
+```
+
+The following patterns are *not* considered violations:
+
+```css
+a {
+ width: 10px;
+}
+```
+
+```css
+a {
+ width: 10Px;
+}
+```
+
+```css
+a {
+ width: 10pX;
+}
+```
+
+```css
+a {
+ width: calc(10px + 10px);
+}
+```
+
+## Optional secondary options
+
+### `ignoreUnits: ["/regex/", "string"]`
+
+Given:
+
+```js
+["/^my-/", "custom"]
+```
+
+The following patterns are *not* considered violations:
+
+```css
+a {
+ width: 10custom;
+}
+```
+
+```css
+a {
+ width: 10my-unit;
+}
+```
+
+```css
+a {
+ width: 10my-other-unit;
+}
+```