--- /dev/null
+# selector-pseudo-element-case
+
+Specify lowercase or uppercase for pseudo-element selectors.
+
+```css
+ a::before {}
+/** ↑
+ * This is pseudo-element selector */
+```
+
+## Options
+
+`string`: `"lower"|"upper"`
+
+### `"lower"`
+
+The following patterns are considered violations:
+
+```css
+a:Before {}
+```
+
+```css
+a:bEfOrE {}
+```
+
+```css
+a:BEFORE {}
+```
+
+```css
+a::Before {}
+```
+
+```css
+a::bEfOrE {}
+```
+
+```css
+a::BEFORE {}
+```
+
+```css
+input::-MOZ-PLACEHOLDER {}
+```
+
+The following patterns are *not* considered violations:
+
+```css
+a:before {}
+```
+
+```css
+a::before {}
+```
+
+```css
+input::-moz-placeholder {}
+```
+
+### `"upper"`
+
+The following patterns are considered violations:
+
+```css
+a:Before {}
+```
+
+```css
+a:bEfOrE {}
+```
+
+```css
+a:BEFORE {}
+```
+
+```css
+a::Before {}
+```
+
+```css
+a::bEfOrE {}
+```
+
+```css
+a::before {}
+```
+
+```css
+input::-moz-placeholder {}
+```
+
+The following patterns are *not* considered violations:
+
+```css
+a:BEFORE {}
+```
+
+```css
+a::BEFORE {}
+```
+
+```css
+input::-MOZ-PLACEHOLDER {}
+```