4 files changed, 12 insertions, 0 deletions
diff --git a/Userland/Libraries/LibWeb/CSS/Parser/DeprecatedCSSParser.cpp b/Userland/Libraries/LibWeb/CSS/Parser/DeprecatedCSSParser.cpp
index 365ed0eee2..a64bcfbae8 100644
--- a/Userland/Libraries/LibWeb/CSS/Parser/DeprecatedCSSParser.cpp
+++ b/Userland/Libraries/LibWeb/CSS/Parser/DeprecatedCSSParser.cpp
@@ -554,6 +554,8 @@ public:
                 simple_selector.pseudo_class = CSS::Selector::SimpleSelector::PseudoClass::Empty;
             } else if (pseudo_name.equals_ignoring_case("root")) {
                 simple_selector.pseudo_class = CSS::Selector::SimpleSelector::PseudoClass::Root;
+            } else if (pseudo_name.equals_ignoring_case("first-of-type")) {
+                simple_selector.pseudo_class = CSS::Selector::SimpleSelector::PseudoClass::FirstOfType;
             } else if (pseudo_name.equals_ignoring_case("before")) {
                 simple_selector.pseudo_element = CSS::Selector::SimpleSelector::PseudoElement::Before;
             } else if (pseudo_name.equals_ignoring_case("after")) {
diff --git a/Userland/Libraries/LibWeb/CSS/Selector.h b/Userland/Libraries/LibWeb/CSS/Selector.h
index d5dae94f98..e9d0085206 100644
--- a/Userland/Libraries/LibWeb/CSS/Selector.h
+++ b/Userland/Libraries/LibWeb/CSS/Selector.h
@@ -54,6 +54,7 @@ public:
             OnlyChild,
             Empty,
             Root,
+            FirstOfType,
         };
         PseudoClass pseudo_class { PseudoClass::None };
 
diff --git a/Userland/Libraries/LibWeb/CSS/SelectorEngine.cpp b/Userland/Libraries/LibWeb/CSS/SelectorEngine.cpp
index a1db87f78f..96c0743f89 100644
--- a/Userland/Libraries/LibWeb/CSS/SelectorEngine.cpp
+++ b/Userland/Libraries/LibWeb/CSS/SelectorEngine.cpp
@@ -90,6 +90,12 @@ static bool matches(const CSS::Selector::SimpleSelector& component, const DOM::E
         if (!is<HTML::HTMLElement>(element))
             return false;
         break;
+    case CSS::Selector::SimpleSelector::PseudoClass::FirstOfType:
+        for (auto* sibling = element.previous_element_sibling(); sibling; sibling = sibling->previous_element_sibling()) {
+            if (sibling->tag_name() == element.tag_name())
+                return false;
+        }
+        break;
     }
 
     switch (component.attribute_match_type) {
diff --git a/Userland/Libraries/LibWeb/Dump.cpp b/Userland/Libraries/LibWeb/Dump.cpp
index 1be93503a7..cdb5297fb8 100644
--- a/Userland/Libraries/LibWeb/Dump.cpp
+++ b/Userland/Libraries/LibWeb/Dump.cpp
@@ -359,6 +359,9 @@ void dump_selector(StringBuilder& builder, const CSS::Selector& selector)
             case CSS::Selector::SimpleSelector::PseudoClass::Root:
                 pseudo_class_description = "Root";
                 break;
+            case CSS::Selector::SimpleSelector::PseudoClass::FirstOfType:
+                pseudo_class_description = "FirstOfType";
+                break;
             case CSS::Selector::SimpleSelector::PseudoClass::Focus:
                 pseudo_class_description = "Focus";
                 break;