diff --git a/README.md b/README.md
index 761a942b..f7b16e6f 100644
--- a/README.md
+++ b/README.md
@@ -124,6 +124,8 @@ information on what to include when reporting a bug.
  - Added `GLFW_RESIZE_EW_CURSOR` alias for `GLFW_HRESIZE_CURSOR` (#427)
  - Added `GLFW_RESIZE_NS_CURSOR` alias for `GLFW_VRESIZE_CURSOR` (#427)
  - Added `GLFW_POINTING_HAND_CURSOR` alias for `GLFW_HAND_CURSOR` (#427)
+ - Added `GLFW_FEATURE_UNAVAILABLE` error for platform limitations (#1692)
+ - Added `GLFW_FEATURE_UNIMPLEMENTED` error for incomplete backends (#1692)
  - Updated the minimum required CMake version to 3.1
  - Disabled tests and examples by default when built as a CMake subdirectory
  - Bugfix: The CMake config-file package used an absolute path and was not
diff --git a/include/GLFW/glfw3.h b/include/GLFW/glfw3.h
index 9893e359..6db5b579 100644
--- a/include/GLFW/glfw3.h
+++ b/include/GLFW/glfw3.h
@@ -783,6 +783,33 @@ extern "C" {
  *  [custom cursor](@ref cursor_custom).
  */
 #define GLFW_CURSOR_UNAVAILABLE     0x0001000B
+/*! @brief The reuqested feature is not provided by the platform.
+ *
+ *  The requested feature is not provided by the platform, so GLFW is unable to
+ *  implement it.  The documentation for each function notes if it could emit
+ *  this error.
+ *
+ *  @analysis Platform or platform version limitation.  The error can be ignored
+ *  unless the feature is critical to the application.
+ *
+ *  @par
+ *  A function call that emits this error has no effect other than the error and
+ *  updating any existing out parameters.
+ */
+#define GLFW_FEATURE_UNAVAILABLE    0x0001000C
+/*! @brief The requested feature is not implemented for the platform.
+ *
+ *  The requested feature has not yet been implemented in GLFW for this platform.
+ *
+ *  @analysis An incomplete implementation of GLFW for this platform, hopefully
+ *  fixed in a future release.  The error can be ignored unless the feature is
+ *  critical to the application.
+ *
+ *  @par
+ *  A function call that emits this error has no effect other than the error and
+ *  updating any existing out parameters.
+ */
+#define GLFW_FEATURE_UNIMPLEMENTED  0x0001000D
 /*! @} */
 
 /*! @addtogroup window
@@ -2871,21 +2898,21 @@ GLFWAPI void glfwSetWindowTitle(GLFWwindow* window, const char* title);
  *  @param[in] images The images to create the icon from.  This is ignored if
  *  count is zero.
  *
- *  @errors Possible errors include @ref GLFW_NOT_INITIALIZED and @ref
- *  GLFW_PLATFORM_ERROR.
+ *  @errors Possible errors include @ref GLFW_NOT_INITIALIZED, @ref
+ *  GLFW_PLATFORM_ERROR and @ref GLFW_FEATURE_UNAVAILABLE (see remarks).
  *
  *  @pointer_lifetime The specified image data is copied before this function
  *  returns.
  *
- *  @remark @macos The GLFW window has no icon, as it is not a document
- *  window, so this function does nothing.  The dock icon will be the same as
+ *  @remark @macos Regular windows do not have icons on macOS.  This function
+ *  will emit @ref GLFW_FEATURE_UNAVAILABLE.  The dock icon will be the same as
  *  the application bundle's icon.  For more information on bundles, see the
  *  [Bundle Programming Guide](https://developer.apple.com/library/mac/documentation/CoreFoundation/Conceptual/CFBundles/)
  *  in the Mac Developer Library.
  *
  *  @remark @wayland There is no existing protocol to change an icon, the
  *  window will thus inherit the one defined in the application's desktop file.
- *  This function always emits @ref GLFW_PLATFORM_ERROR.
+ *  This function will emit @ref GLFW_FEATURE_UNAVAILABLE.
  *
  *  @thread_safety This function must only be called from the main thread.
  *
@@ -2911,12 +2938,12 @@ GLFWAPI void glfwSetWindowIcon(GLFWwindow* window, int count, const GLFWimage* i
  *  @param[out] ypos Where to store the y-coordinate of the upper-left corner of
  *  the content area, or `NULL`.
  *
- *  @errors Possible errors include @ref GLFW_NOT_INITIALIZED and @ref
- *  GLFW_PLATFORM_ERROR.
+ *  @errors Possible errors include @ref GLFW_NOT_INITIALIZED, @ref
+ *  GLFW_PLATFORM_ERROR and @ref GLFW_FEATURE_UNAVAILABLE (see remarks).
  *
  *  @remark @wayland There is no way for an application to retrieve the global
- *  position of its windows, this function will always emit @ref
- *  GLFW_PLATFORM_ERROR.
+ *  position of its windows.  This function will emit @ref
+ *  GLFW_FEATURE_UNAVAILABLE.
  *
  *  @thread_safety This function must only be called from the main thread.
  *
@@ -2945,12 +2972,12 @@ GLFWAPI void glfwGetWindowPos(GLFWwindow* window, int* xpos, int* ypos);
  *  @param[in] xpos The x-coordinate of the upper-left corner of the content area.
  *  @param[in] ypos The y-coordinate of the upper-left corner of the content area.
  *
- *  @errors Possible errors include @ref GLFW_NOT_INITIALIZED and @ref
- *  GLFW_PLATFORM_ERROR.
+ *  @errors Possible errors include @ref GLFW_NOT_INITIALIZED, @ref
+ *  GLFW_PLATFORM_ERROR and @ref GLFW_FEATURE_UNAVAILABLE (see remarks).
  *
  *  @remark @wayland There is no way for an application to set the global
- *  position of its windows, this function will always emit @ref
- *  GLFW_PLATFORM_ERROR.
+ *  position of its windows.  This function will emit @ref
+ *  GLFW_FEATURE_UNAVAILABLE.
  *
  *  @thread_safety This function must only be called from the main thread.
  *
@@ -3262,8 +3289,11 @@ GLFWAPI float glfwGetWindowOpacity(GLFWwindow* window);
  *  @param[in] window The window to set the opacity for.
  *  @param[in] opacity The desired opacity of the specified window.
  *
- *  @errors Possible errors include @ref GLFW_NOT_INITIALIZED and @ref
- *  GLFW_PLATFORM_ERROR.
+ *  @errors Possible errors include @ref GLFW_NOT_INITIALIZED, @ref
+ *  GLFW_PLATFORM_ERROR and @ref GLFW_FEATURE_UNAVAILABLE (see remarks).
+ *
+ *  @remark @wayland There is no way to set an opacity factor for a window.
+ *  This function will emit @ref GLFW_FEATURE_UNAVAILABLE.
  *
  *  @thread_safety This function must only be called from the main thread.
  *
@@ -3430,11 +3460,11 @@ GLFWAPI void glfwHideWindow(GLFWwindow* window);
  *
  *  @param[in] window The window to give input focus.
  *
- *  @errors Possible errors include @ref GLFW_NOT_INITIALIZED and @ref
- *  GLFW_PLATFORM_ERROR.
+ *  @errors Possible errors include @ref GLFW_NOT_INITIALIZED, @ref
+ *  GLFW_PLATFORM_ERROR and @ref GLFW_FEATURE_UNAVAILABLE (see remarks).
  *
- *  @remark @wayland It is not possible for an application to bring its windows
- *  to front, this function will always emit @ref GLFW_PLATFORM_ERROR.
+ *  @remark @wayland It is not possible for an application to set the input
+ *  focus.  This function will emit @ref GLFW_FEATURE_UNAVAILABLE.
  *
  *  @thread_safety This function must only be called from the main thread.
  *
@@ -4186,7 +4216,7 @@ GLFWAPI int glfwGetInputMode(GLFWwindow* window, int mode);
  *  If the mode is `GLFW_RAW_MOUSE_MOTION`, the value must be either `GLFW_TRUE`
  *  to enable raw (unscaled and unaccelerated) mouse motion when the cursor is
  *  disabled, or `GLFW_FALSE` to disable it.  If raw motion is not supported,
- *  attempting to set this will emit @ref GLFW_PLATFORM_ERROR.  Call @ref
+ *  attempting to set this will emit @ref GLFW_FEATURE_UNAVAILABLE.  Call @ref
  *  glfwRawMouseMotionSupported to check for support.
  *
  *  @param[in] window The window whose input mode to set.
@@ -4196,7 +4226,8 @@ GLFWAPI int glfwGetInputMode(GLFWwindow* window, int mode);
  *  @param[in] value The new value of the specified input mode.
  *
  *  @errors Possible errors include @ref GLFW_NOT_INITIALIZED, @ref
- *  GLFW_INVALID_ENUM and @ref GLFW_PLATFORM_ERROR.
+ *  GLFW_INVALID_ENUM, @ref GLFW_PLATFORM_ERROR and @ref
+ *  GLFW_FEATURE_UNAVAILABLE (see above).
  *
  *  @thread_safety This function must only be called from the main thread.
  *
diff --git a/src/cocoa_window.m b/src/cocoa_window.m
index 7b50c753..b7a18cad 100644
--- a/src/cocoa_window.m
+++ b/src/cocoa_window.m
@@ -982,7 +982,8 @@ void _glfwPlatformSetWindowTitle(_GLFWwindow* window, const char* title)
 void _glfwPlatformSetWindowIcon(_GLFWwindow* window,
                                 int count, const GLFWimage* images)
 {
-    // Regular windows do not have icons
+    _glfwInputError(GLFW_FEATURE_UNAVAILABLE,
+                    "Cocoa: Regular windows do not have icons on macOS");
 }
 
 void _glfwPlatformGetWindowPos(_GLFWwindow* window, int* xpos, int* ypos)
@@ -1376,6 +1377,8 @@ void _glfwPlatformSetWindowOpacity(_GLFWwindow* window, float opacity)
 
 void _glfwPlatformSetRawMouseMotion(_GLFWwindow *window, GLFWbool enabled)
 {
+    _glfwInputError(GLFW_FEATURE_UNIMPLEMENTED,
+                    "Cocoa: Raw mouse motion not yet implemented");
 }
 
 GLFWbool _glfwPlatformRawMouseMotionSupported(void)
diff --git a/src/init.c b/src/init.c
index 13baff70..d23bbfa9 100644
--- a/src/init.c
+++ b/src/init.c
@@ -191,6 +191,10 @@ void _glfwInputError(int code, const char* format, ...)
             strcpy(description, "The specified window has no context");
         else if (code == GLFW_CURSOR_UNAVAILABLE)
             strcpy(description, "The specified cursor shape is unavailable");
+        else if (code == GLFW_FEATURE_UNAVAILABLE)
+            strcpy(description, "The requested feature cannot be implemented for this platform");
+        else if (code == GLFW_FEATURE_UNIMPLEMENTED)
+            strcpy(description, "The requested feature has not yet been implemented for this platform");
         else
             strcpy(description, "ERROR: UNKNOWN GLFW ERROR");
     }
diff --git a/src/wl_monitor.c b/src/wl_monitor.c
index 55f62015..a6356de0 100644
--- a/src/wl_monitor.c
+++ b/src/wl_monitor.c
@@ -199,7 +199,7 @@ void _glfwPlatformGetVideoMode(_GLFWmonitor* monitor, GLFWvidmode* mode)
 
 GLFWbool _glfwPlatformGetGammaRamp(_GLFWmonitor* monitor, GLFWgammaramp* ramp)
 {
-    _glfwInputError(GLFW_PLATFORM_ERROR,
+    _glfwInputError(GLFW_FEATURE_UNAVAILABLE,
                     "Wayland: Gamma ramp access is not available");
     return GLFW_FALSE;
 }
@@ -207,7 +207,7 @@ GLFWbool _glfwPlatformGetGammaRamp(_GLFWmonitor* monitor, GLFWgammaramp* ramp)
 void _glfwPlatformSetGammaRamp(_GLFWmonitor* monitor,
                                const GLFWgammaramp* ramp)
 {
-    _glfwInputError(GLFW_PLATFORM_ERROR,
+    _glfwInputError(GLFW_FEATURE_UNAVAILABLE,
                     "Wayland: Gamma ramp access is not available");
 }
 
diff --git a/src/wl_window.c b/src/wl_window.c
index 26cb2ac1..a6d5569c 100644
--- a/src/wl_window.c
+++ b/src/wl_window.c
@@ -883,8 +883,8 @@ void _glfwPlatformSetWindowTitle(_GLFWwindow* window, const char* title)
 void _glfwPlatformSetWindowIcon(_GLFWwindow* window,
                                 int count, const GLFWimage* images)
 {
-    _glfwInputError(GLFW_PLATFORM_ERROR,
-                    "Wayland: Setting window icon not supported");
+    _glfwInputError(GLFW_FEATURE_UNAVAILABLE,
+                    "Wayland: The platform does not support setting the window icon");
 }
 
 void _glfwPlatformGetWindowPos(_GLFWwindow* window, int* xpos, int* ypos)
@@ -892,16 +892,16 @@ void _glfwPlatformGetWindowPos(_GLFWwindow* window, int* xpos, int* ypos)
     // A Wayland client is not aware of its position, so just warn and leave it
     // as (0, 0)
 
-    _glfwInputError(GLFW_PLATFORM_ERROR,
-                    "Wayland: Window position retrieval not supported");
+    _glfwInputError(GLFW_FEATURE_UNAVAILABLE,
+                    "Wayland: The platform does not provide the window position");
 }
 
 void _glfwPlatformSetWindowPos(_GLFWwindow* window, int xpos, int ypos)
 {
     // A Wayland client can not set its position, so just warn
 
-    _glfwInputError(GLFW_PLATFORM_ERROR,
-                    "Wayland: Window position setting not supported");
+    _glfwInputError(GLFW_FEATURE_UNAVAILABLE,
+                    "Wayland: The platform does not support setting the window position");
 }
 
 void _glfwPlatformGetWindowSize(_GLFWwindow* window, int* width, int* height)
@@ -940,6 +940,8 @@ void _glfwPlatformSetWindowAspectRatio(_GLFWwindow* window,
 {
     // TODO: find out how to trigger a resize.
     // The actual limits are checked in the xdg_toplevel::configure handler.
+    _glfwInputError(GLFW_FEATURE_UNIMPLEMENTED,
+                    "Wayland: Window aspect ratio not yet implemented");
 }
 
 void _glfwPlatformGetFramebufferSize(_GLFWwindow* window,
@@ -1030,14 +1032,14 @@ void _glfwPlatformHideWindow(_GLFWwindow* window)
 void _glfwPlatformRequestWindowAttention(_GLFWwindow* window)
 {
     // TODO
-    _glfwInputError(GLFW_PLATFORM_ERROR,
+    _glfwInputError(GLFW_FEATURE_UNIMPLEMENTED,
                     "Wayland: Window attention request not implemented yet");
 }
 
 void _glfwPlatformFocusWindow(_GLFWwindow* window)
 {
-    _glfwInputError(GLFW_PLATFORM_ERROR,
-                    "Wayland: Focusing a window requires user interaction");
+    _glfwInputError(GLFW_FEATURE_UNAVAILABLE,
+                    "Wayland: The platform does not support setting the input focus");
 }
 
 void _glfwPlatformSetWindowMonitor(_GLFWwindow* window,
@@ -1096,7 +1098,7 @@ int _glfwPlatformFramebufferTransparent(_GLFWwindow* window)
 void _glfwPlatformSetWindowResizable(_GLFWwindow* window, GLFWbool enabled)
 {
     // TODO
-    _glfwInputError(GLFW_PLATFORM_ERROR,
+    _glfwInputError(GLFW_FEATURE_UNIMPLEMENTED,
                     "Wayland: Window attribute setting not implemented yet");
 }
 
@@ -1114,7 +1116,7 @@ void _glfwPlatformSetWindowDecorated(_GLFWwindow* window, GLFWbool enabled)
 void _glfwPlatformSetWindowFloating(_GLFWwindow* window, GLFWbool enabled)
 {
     // TODO
-    _glfwInputError(GLFW_PLATFORM_ERROR,
+    _glfwInputError(GLFW_FEATURE_UNIMPLEMENTED,
                     "Wayland: Window attribute setting not implemented yet");
 }
 
@@ -1125,6 +1127,8 @@ float _glfwPlatformGetWindowOpacity(_GLFWwindow* window)
 
 void _glfwPlatformSetWindowOpacity(_GLFWwindow* window, float opacity)
 {
+    _glfwInputError(GLFW_FEATURE_UNAVAILABLE,
+                    "Wayland: The platform does not support setting the window opacity");
 }
 
 void _glfwPlatformSetRawMouseMotion(_GLFWwindow *window, GLFWbool enabled)
@@ -1186,6 +1190,8 @@ void _glfwPlatformSetCursorMode(_GLFWwindow* window, int mode)
 const char* _glfwPlatformGetScancodeName(int scancode)
 {
     // TODO
+    _glfwInputError(GLFW_FEATURE_UNIMPLEMENTED,
+                    "Wayland: Key names not yet implemented");
     return NULL;
 }