diff --git a/src/lang/english.txt b/src/lang/english.txt
--- a/src/lang/english.txt
+++ b/src/lang/english.txt
@@ -230,6 +230,7 @@ STR_BUTTON_RENAME                       
 STR_TOOLTIP_CLOSE_WINDOW                                        :{BLACK}Close window
 STR_TOOLTIP_WINDOW_TITLE_DRAG_THIS                              :{BLACK}Window title - drag this to move window
 STR_TOOLTIP_SHADE                                               :{BLACK}Shade window - only show the title bar
+STR_TOOLTIP_DEBUG                                               :{BLACK}Show NewGRF debug information
 STR_TOOLTIP_STICKY                                              :{BLACK}Mark this window as uncloseable by the 'Close All Windows' key
 STR_TOOLTIP_RESIZE                                              :{BLACK}Click and drag to resize this window
 STR_TOOLTIP_TOGGLE_LARGE_SMALL_WINDOW                           :{BLACK}Toggle large/small window size
diff --git a/src/widget.cpp b/src/widget.cpp
--- a/src/widget.cpp
+++ b/src/widget.cpp
@@ -17,6 +17,7 @@
 #include "strings_func.h"
 #include "transparency.h"
 #include "core/geometry_func.hpp"
+#include "settings_type.h"
 
 #include "table/sprites.h"
 #include "table/strings.h"
@@ -477,6 +478,18 @@ static inline void DrawStickyBox(const R
 }
 
 /**
+ * Draw a NewGRF debug box.
+ * @param r       Rectangle of the box.
+ * @param colour  Colour of the debug box.
+ * @param clicked Box is lowered.
+ */
+static inline void DrawDebugBox(const Rect &r, Colours colour, bool clicked)
+{
+	DrawFrameRect(r.left, r.top, r.right, r.bottom, colour, (clicked) ? FR_LOWERED : FR_NONE);
+	DrawSprite(SPR_WINDOW_DEBUG, PAL_NONE, r.left + WD_DEBUGBOX_LEFT + clicked, r.top + WD_DEBUGBOX_TOP + clicked);
+}
+
+/**
  * Draw a resize box.
  * @param r       Rectangle of the box.
  * @param colour  Colour of the resize box.
@@ -1690,12 +1703,14 @@ void NWidgetViewport::UpdateViewportCoor
 /* static */ void NWidgetLeaf::InvalidateDimensionCache()
 {
 	shadebox_dimension.width  = shadebox_dimension.height  = 0;
+	debugbox_dimension.width  = debugbox_dimension.height  = 0;
 	stickybox_dimension.width = stickybox_dimension.height = 0;
 	resizebox_dimension.width = resizebox_dimension.height = 0;
 	closebox_dimension.width  = closebox_dimension.height  = 0;
 }
 
 Dimension NWidgetLeaf::shadebox_dimension  = {0, 0};
+Dimension NWidgetLeaf::debugbox_dimension  = {0, 0};
 Dimension NWidgetLeaf::stickybox_dimension = {0, 0};
 Dimension NWidgetLeaf::resizebox_dimension = {0, 0};
 Dimension NWidgetLeaf::closebox_dimension  = {0, 0};
@@ -1710,7 +1725,7 @@ Dimension NWidgetLeaf::closebox_dimensio
  */
 NWidgetLeaf::NWidgetLeaf(WidgetType tp, Colours colour, int index, uint16 data, StringID tip) : NWidgetCore(tp, colour, 1, 1, data, tip)
 {
-	assert(index >= 0 || tp == WWT_LABEL || tp == WWT_TEXT || tp == WWT_CAPTION || tp == WWT_RESIZEBOX || tp == WWT_SHADEBOX || tp == WWT_STICKYBOX || tp == WWT_CLOSEBOX);
+	assert(index >= 0 || tp == WWT_LABEL || tp == WWT_TEXT || tp == WWT_CAPTION || tp == WWT_RESIZEBOX || tp == WWT_SHADEBOX || tp == WWT_DEBUGBOX || tp == WWT_STICKYBOX || tp == WWT_CLOSEBOX);
 	if (index >= 0) this->SetIndex(index);
 	this->SetMinimalSize(0, 0);
 	this->SetResize(0, 0);
@@ -1775,6 +1790,12 @@ NWidgetLeaf::NWidgetLeaf(WidgetType tp, 
 			this->SetDataTip(STR_NULL, STR_TOOLTIP_SHADE);
 			break;
 
+		case WWT_DEBUGBOX:
+			this->SetFill(0, 0);
+			this->SetMinimalSize(WD_DEBUGBOX_TOP, 14);
+			this->SetDataTip(STR_NULL, STR_TOOLTIP_DEBUG);
+			break;
+
 		case WWT_RESIZEBOX:
 			this->SetFill(0, 0);
 			this->SetMinimalSize(WD_RESIZEBOX_WIDTH, 12);
@@ -1834,6 +1855,24 @@ void NWidgetLeaf::SetupSmallestSize(Wind
 			size = maxdim(size, NWidgetLeaf::shadebox_dimension);
 			break;
 		}
+		case WWT_DEBUGBOX:
+			if (_settings_client.gui.newgrf_developer_tools && w->IsNewGRFInspectable()) {
+				static const Dimension extra = {WD_DEBUGBOX_LEFT + WD_DEBUGBOX_RIGHT, WD_DEBUGBOX_TOP + WD_DEBUGBOX_BOTTOM};
+				padding = &extra;
+				if (NWidgetLeaf::debugbox_dimension.width == 0) {
+					NWidgetLeaf::debugbox_dimension = GetSpriteSize(SPR_WINDOW_DEBUG);
+					NWidgetLeaf::debugbox_dimension.width += extra.width;
+					NWidgetLeaf::debugbox_dimension.height += extra.height;
+				}
+				size = maxdim(size, NWidgetLeaf::debugbox_dimension);
+			} else {
+				/* If the setting is disabled we don't want to see it! */
+				size.width = 0;
+				fill.width = 0;
+				resize.width = 0;
+			}
+			break;
+
 		case WWT_STICKYBOX: {
 			static const Dimension extra = {WD_STICKYBOX_LEFT + WD_STICKYBOX_RIGHT, WD_STICKYBOX_TOP + WD_STICKYBOX_BOTTOM};
 			padding = &extra;
@@ -2050,6 +2089,10 @@ void NWidgetLeaf::Draw(const Window *w)
 			DrawShadeBox(r, this->colour, w->IsShaded());
 			break;
 
+		case WWT_DEBUGBOX:
+			DrawDebugBox(r, this->colour, clicked);
+			break;
+
 		case WWT_STICKYBOX:
 			assert(this->widget_data == 0);
 			DrawStickyBox(r, this->colour, !!(w->flags4 & WF_STICKY));
diff --git a/src/widget_type.h b/src/widget_type.h
--- a/src/widget_type.h
+++ b/src/widget_type.h
@@ -65,6 +65,7 @@ enum WidgetType {
 	WWT_HSCROLLBAR, ///< Horizontal scrollbar
 	WWT_SHADEBOX,   ///< Shade box (at top-right of a window, between caption and stickybox)
 	WWT_STICKYBOX,  ///< Sticky box (normally at top-right of a window)
+	WWT_DEBUGBOX,   ///< NewGRF debug box (between shade box and caption)
 	WWT_SCROLL2BAR, ///< 2nd vertical scrollbar
 	WWT_RESIZEBOX,  ///< Resize box (normally at bottom-right of a window)
 	WWT_CLOSEBOX,   ///< Close box (at top-left of a window)
@@ -480,6 +481,7 @@ public:
 	static void InvalidateDimensionCache();
 private:
 	static Dimension shadebox_dimension;  ///< Cached size of a shadebox widget.
+	static Dimension debugbox_dimension;  ///< Cached size of a debugbox widget.
 	static Dimension stickybox_dimension; ///< Cached size of a stickybox widget.
 	static Dimension resizebox_dimension; ///< Cached size of a resizebox widget.
 	static Dimension closebox_dimension;  ///< Cached size of a closebox widget.
diff --git a/src/window.cpp b/src/window.cpp
--- a/src/window.cpp
+++ b/src/window.cpp
@@ -346,6 +346,10 @@ static void DispatchLeftClickEvent(Windo
 			nw->SetDirty(w);
 			return;
 
+		case WWT_DEBUGBOX:
+			w->ShowNewGRFInspectWindow();
+			break;
+
 		case WWT_SHADEBOX:
 			nw->SetDirty(w);
 			w->SetShaded(!w->IsShaded());
diff --git a/src/window_gui.h b/src/window_gui.h
--- a/src/window_gui.h
+++ b/src/window_gui.h
@@ -85,6 +85,13 @@ enum WidgetDrawDistances {
 	WD_STICKYBOX_TOP    = 3,    ///< Top offset of sticky sprite.
 	WD_STICKYBOX_BOTTOM = 3,    ///< Bottom offset of sticky sprite.
 
+	/* WWT_DEBUGBOX */
+	WD_DEBUGBOX_WIDTH  = 12,    ///< Width of a standard debug box widget.
+	WD_DEBUGBOX_LEFT   = 2,     ///< Left offset of debug sprite.
+	WD_DEBUGBOX_RIGHT  = 2,     ///< Right offset of debug sprite.
+	WD_DEBUGBOX_TOP    = 3,     ///< Top offset of debug sprite.
+	WD_DEBUGBOX_BOTTOM = 3,     ///< Bottom offset of debug sprite.
+
 	/* WWT_RESIZEBOX */
 	WD_RESIZEBOX_WIDTH  = 12,   ///< Width of a resize box widget.
 	WD_RESIZEBOX_LEFT   = 3,    ///< Left offset of resize sprite.
@@ -770,6 +777,20 @@ public:
 	virtual void OnPlacePresize(Point pt, TileIndex tile) {}
 
 	/*** End of the event handling ***/
+
+	/**
+	 * Is the data related to this window NewGRF inspectable?
+	 * @return true iff it is inspectable.
+	 */
+	virtual bool IsNewGRFInspectable() const { return false; }
+
+	/**
+	 * Show the NewGRF inspection window. When this function is called it is
+	 * up to the window to call and pass the right parameters to the
+	 * ShowInspectWindow function.
+	 * @pre this->IsNewGRFInspectable()
+	 */
+	virtual void ShowNewGRFInspectWindow() const { NOT_REACHED(); }
 };
 
 /** Get the nested widget with number \a widnum from the nested widget tree.