diff --git a/Userland/Libraries/LibAudio/Loader.h b/Userland/Libraries/LibAudio/Loader.h
index bb2e2f342fa..af72d0e1857 100644
--- a/Userland/Libraries/LibAudio/Loader.h
+++ b/Userland/Libraries/LibAudio/Loader.h
@@ -30,6 +30,7 @@
 #include <AK/RefCounted.h>
 #include <AK/RefPtr.h>
 #include <AK/StringView.h>
+#include <LibAudio/Buffer.h>
 #include <LibCore/File.h>
 
 namespace Audio {
diff --git a/Userland/Libraries/LibC/sys/un.h b/Userland/Libraries/LibC/sys/un.h
index e0df3061530..1981f6c4bca 100644
--- a/Userland/Libraries/LibC/sys/un.h
+++ b/Userland/Libraries/LibC/sys/un.h
@@ -26,6 +26,7 @@
 
 #pragma once
 
+#include <bits/stdint.h>
 #include <sys/cdefs.h>
 
 __BEGIN_DECLS
diff --git a/Userland/Libraries/LibELF/Validation.h b/Userland/Libraries/LibELF/Validation.h
index fe49c80b820..e5bc75eff9e 100644
--- a/Userland/Libraries/LibELF/Validation.h
+++ b/Userland/Libraries/LibELF/Validation.h
@@ -26,6 +26,7 @@
 
 #pragma once
 
+#include <AK/String.h>
 #include <LibELF/exec_elf.h>
 
 namespace ELF {
diff --git a/Userland/Libraries/LibGUI/DragOperation.h b/Userland/Libraries/LibGUI/DragOperation.h
index 8595c0a8484..d9c0e03b210 100644
--- a/Userland/Libraries/LibGUI/DragOperation.h
+++ b/Userland/Libraries/LibGUI/DragOperation.h
@@ -27,6 +27,7 @@
 #pragma once
 
 #include <AK/OwnPtr.h>
+#include <LibCore/MimeData.h>
 #include <LibCore/Object.h>
 #include <LibGUI/Forward.h>
 #include <LibGfx/Forward.h>
diff --git a/Userland/Libraries/LibGUI/FontPicker.h b/Userland/Libraries/LibGUI/FontPicker.h
index 89ba8143f62..b27a867cdff 100644
--- a/Userland/Libraries/LibGUI/FontPicker.h
+++ b/Userland/Libraries/LibGUI/FontPicker.h
@@ -27,6 +27,7 @@
 #pragma once
 
 #include <LibGUI/Dialog.h>
+#include <LibGfx/Font.h>
 #include <LibGfx/Forward.h>
 
 namespace GUI {
diff --git a/Userland/Libraries/LibGUI/ModelIndex.h b/Userland/Libraries/LibGUI/ModelIndex.h
index 5f8e088798a..4d6d49a92b6 100644
--- a/Userland/Libraries/LibGUI/ModelIndex.h
+++ b/Userland/Libraries/LibGUI/ModelIndex.h
@@ -26,6 +26,7 @@
 
 #pragma once
 
+#include <AK/Format.h>
 #include <AK/Traits.h>
 #include <LibGUI/Forward.h>
 #include <LibGUI/ModelRole.h>
diff --git a/Userland/Libraries/LibGfx/ImageDecoder.h b/Userland/Libraries/LibGfx/ImageDecoder.h
index a054f524a92..b0e1d2c8cf2 100644
--- a/Userland/Libraries/LibGfx/ImageDecoder.h
+++ b/Userland/Libraries/LibGfx/ImageDecoder.h
@@ -30,6 +30,7 @@
 #include <AK/OwnPtr.h>
 #include <AK/RefCounted.h>
 #include <AK/RefPtr.h>
+#include <LibGfx/Bitmap.h>
 #include <LibGfx/Size.h>
 
 namespace Gfx {
diff --git a/Userland/Libraries/LibLine/Span.h b/Userland/Libraries/LibLine/Span.h
index 0d1eb108f81..b42a8047fae 100644
--- a/Userland/Libraries/LibLine/Span.h
+++ b/Userland/Libraries/LibLine/Span.h
@@ -26,6 +26,8 @@
 
 #pragma once
 
+#include <stddef.h>
+
 namespace Line {
 
 class Span {
diff --git a/Userland/Libraries/LibTTF/Cmap.h b/Userland/Libraries/LibTTF/Cmap.h
index 2133a72f91d..bde8513c47b 100644
--- a/Userland/Libraries/LibTTF/Cmap.h
+++ b/Userland/Libraries/LibTTF/Cmap.h
@@ -27,6 +27,7 @@
 #pragma once
 
 #include <AK/Span.h>
+#include <stdint.h>
 
 namespace TTF {
 
diff --git a/Userland/Libraries/LibWeb/DOM/EventDispatcher.h b/Userland/Libraries/LibWeb/DOM/EventDispatcher.h
index c5c380c5976..ecfaba67e63 100644
--- a/Userland/Libraries/LibWeb/DOM/EventDispatcher.h
+++ b/Userland/Libraries/LibWeb/DOM/EventDispatcher.h
@@ -27,6 +27,7 @@
 #pragma once
 
 #include <AK/Forward.h>
+#include <LibWeb/DOM/Event.h>
 #include <LibWeb/Forward.h>
 
 namespace Web::DOM {
diff --git a/Userland/Libraries/LibWeb/DOM/Timer.h b/Userland/Libraries/LibWeb/DOM/Timer.h
index bdecde92d86..c54c7c755a3 100644
--- a/Userland/Libraries/LibWeb/DOM/Timer.h
+++ b/Userland/Libraries/LibWeb/DOM/Timer.h
@@ -29,6 +29,7 @@
 #include <AK/Forward.h>
 #include <LibCore/Forward.h>
 #include <LibJS/Heap/Handle.h>
+#include <LibJS/Runtime/Function.h>
 #include <LibWeb/Forward.h>
 
 namespace Web::DOM {
diff --git a/Userland/Libraries/LibWeb/FontCache.h b/Userland/Libraries/LibWeb/FontCache.h
index 8cc554a8f46..d4d8fe89ce7 100644
--- a/Userland/Libraries/LibWeb/FontCache.h
+++ b/Userland/Libraries/LibWeb/FontCache.h
@@ -29,6 +29,7 @@
 #include <AK/FlyString.h>
 #include <AK/HashMap.h>
 #include <AK/String.h>
+#include <LibGfx/Font.h>
 #include <LibGfx/Forward.h>
 
 struct FontSelector {
diff --git a/Userland/Libraries/LibWeb/Layout/SVGPathBox.h b/Userland/Libraries/LibWeb/Layout/SVGPathBox.h
index cbfe94b4ec6..dcf63e4a394 100644
--- a/Userland/Libraries/LibWeb/Layout/SVGPathBox.h
+++ b/Userland/Libraries/LibWeb/Layout/SVGPathBox.h
@@ -27,6 +27,7 @@
 #pragma once
 
 #include <LibWeb/Layout/SVGGraphicsBox.h>
+#include <LibWeb/SVG/SVGPathElement.h>
 
 namespace Web::Layout {
 
diff --git a/Userland/Libraries/LibWeb/Page/EditEventHandler.h b/Userland/Libraries/LibWeb/Page/EditEventHandler.h
index 67edb9eff00..015c6d81e98 100644
--- a/Userland/Libraries/LibWeb/Page/EditEventHandler.h
+++ b/Userland/Libraries/LibWeb/Page/EditEventHandler.h
@@ -26,6 +26,7 @@
 
 #pragma once
 
+#include <AK/Types.h>
 #include <LibWeb/Forward.h>
 
 namespace Web {
diff --git a/Userland/Libraries/LibWeb/Page/EventHandler.h b/Userland/Libraries/LibWeb/Page/EventHandler.h
index 7ea12d64612..cc1cc19ade0 100644
--- a/Userland/Libraries/LibWeb/Page/EventHandler.h
+++ b/Userland/Libraries/LibWeb/Page/EventHandler.h
@@ -27,6 +27,7 @@
 #pragma once
 
 #include <AK/Forward.h>
+#include <AK/NonnullOwnPtr.h>
 #include <AK/WeakPtr.h>
 #include <Kernel/API/KeyCode.h>
 #include <LibGUI/Forward.h>
diff --git a/Userland/Libraries/LibWeb/Painting/PaintContext.h b/Userland/Libraries/LibWeb/Painting/PaintContext.h
index f6ba50eb879..8750e896503 100644
--- a/Userland/Libraries/LibWeb/Painting/PaintContext.h
+++ b/Userland/Libraries/LibWeb/Painting/PaintContext.h
@@ -26,6 +26,7 @@
 
 #pragma once
 
+#include <AK/Vector.h>
 #include <LibGfx/Forward.h>
 #include <LibGfx/Palette.h>
 #include <LibGfx/Rect.h>
diff --git a/Userland/Libraries/LibWeb/SVG/SVGContext.h b/Userland/Libraries/LibWeb/SVG/SVGContext.h
index ec7fe72effb..0d63ebc71a9 100644
--- a/Userland/Libraries/LibWeb/SVG/SVGContext.h
+++ b/Userland/Libraries/LibWeb/SVG/SVGContext.h
@@ -26,6 +26,9 @@
 
 #pragma once
 
+#include <AK/Vector.h>
+#include <LibGfx/Color.h>
+
 namespace Web {
 
 class SVGContext {
diff --git a/Userland/Libraries/LibWeb/StylePropertiesModel.h b/Userland/Libraries/LibWeb/StylePropertiesModel.h
index 2c260b62f1a..5299526e704 100644
--- a/Userland/Libraries/LibWeb/StylePropertiesModel.h
+++ b/Userland/Libraries/LibWeb/StylePropertiesModel.h
@@ -28,6 +28,7 @@
 
 #include <AK/NonnullRefPtrVector.h>
 #include <LibGUI/Model.h>
+#include <LibWeb/CSS/StyleProperties.h>
 
 namespace Web {
 
diff --git a/Userland/Libraries/LibX86/ELFSymbolProvider.h b/Userland/Libraries/LibX86/ELFSymbolProvider.h
index f208cec0a08..bdfc6123ca7 100644
--- a/Userland/Libraries/LibX86/ELFSymbolProvider.h
+++ b/Userland/Libraries/LibX86/ELFSymbolProvider.h
@@ -27,6 +27,7 @@
 #pragma once
 
 #include <LibELF/Image.h>
+#include <LibX86/Instruction.h>
 
 namespace X86 {