diff --git a/assets/xsd/cdf.xsd b/assets/xsd/cdf.xsd
index 7f9cd6d..793120a 100644
--- a/assets/xsd/cdf.xsd
+++ b/assets/xsd/cdf.xsd
@@ -23,6 +23,158 @@ at <https://docs.microsoft.com/en-us/previous-versions/windows/internet-explorer
                   elementFormDefault="qualified"
                   xmlns="https://msdn.microsoft.com/workshop/standards/cdf/"
                   xmlns:xs="http://www.w3.org/2001/XMLSchema">
+  <xs:simpleType name="sSizes">
+    <xs:restriction base="xs:string">
+      <xs:enumeration value="Yes">
+        <xs:annotation>
+          <xs:documentation>
+            Default. Active Desktop item can be resized.
+          </xs:documentation>
+        </xs:annotation>
+      </xs:enumeration>
+      <xs:enumeration value="No">
+        <xs:annotation>
+          <xs:documentation>
+            Active Desktop item cannot be resized.
+          </xs:documentation>
+        </xs:annotation>
+      </xs:enumeration>
+    </xs:restriction>
+  </xs:simpleType>
+
+  <xs:simpleType name="OpenAsValue">
+    <xs:restriction base="xs:string">
+      <xs:enumeration value="HTML">
+        <xs:annotation>
+          <xs:documentation>
+            Default. Hosted with iframe elements.
+          </xs:documentation>
+        </xs:annotation>
+      </xs:enumeration>
+      <xs:enumeration value="Image">
+        <xs:annotation>
+          <xs:documentation>
+            Hosted with img elements.
+          </xs:documentation>
+        </xs:annotation>
+      </xs:enumeration>
+    </xs:restriction>
+  </xs:simpleType>
+
+  <xs:complexType name="CANRESIZE">
+    <xs:annotation>
+      <xs:documentation>
+        Indicates whether the user can resize the Microsoft Active Desktop item along both the x and y axes.
+        Should only be used when the USAGE is set to "DesktopComponent".
+      </xs:documentation>
+    </xs:annotation>
+    <xs:attribute name="VALUE" type="sSizes" use="optional" default="Yes">
+      <xs:annotation>
+        <xs:documentation>
+          Optional. String value specifying whether the Active Desktop item can be resized.
+        </xs:documentation>
+      </xs:annotation>
+    </xs:attribute>
+  </xs:complexType>
+
+  <xs:complexType name="CANRESIZEX">
+    <xs:annotation>
+      <xs:documentation>
+        Indicates whether the user can resize the Microsoft Active Desktop item along both the (horizontal) x-axis.
+        Should only be used when the USAGE is set to "DesktopComponent".
+      </xs:documentation>
+    </xs:annotation>
+    <xs:attribute name="VALUE" type="sSizes" use="optional" default="Yes">
+      <xs:annotation>
+        <xs:documentation>
+          Optional. String value specifying whether the Active Desktop item can be resized.
+        </xs:documentation>
+      </xs:annotation>
+    </xs:attribute>
+  </xs:complexType>
+
+  <xs:complexType name="CANRESIZEY">
+    <xs:annotation>
+      <xs:documentation>
+        Indicates whether the user can resize the Microsoft Active Desktop item along both the (vertical) y-axis.
+        Should only be used when the USAGE is set to "DesktopComponent".
+      </xs:documentation>
+    </xs:annotation>
+    <xs:attribute name="VALUE" type="sSizes" use="optional" default="Yes">
+      <xs:annotation>
+        <xs:documentation>
+          Optional. String value specifying whether the Active Desktop item can be resized.
+        </xs:documentation>
+      </xs:annotation>
+    </xs:attribute>
+  </xs:complexType>
+
+  <xs:complexType name="HEIGHT">
+    <xs:annotation>
+      <xs:documentation>
+        Indicates the height of the Microsoft Active Desktop item specified in the ITEM element.
+        Should only be used when the USAGE is set to "DesktopComponent".
+      </xs:documentation>
+    </xs:annotation>
+    <xs:attribute name="VALUE" type="xs:nonNegativeInteger" use="required">
+      <xs:annotation>
+        <xs:documentation>
+          Required. Numeric value specifying the height of the Active Desktop item.
+        </xs:documentation>
+      </xs:annotation>
+    </xs:attribute>
+  </xs:complexType>
+
+  <xs:complexType name="OPENAS">
+    <xs:annotation>
+      <xs:documentation>
+        Indicates the content type of the Microsoft Active Desktop item specified in the ITEM element.
+        Should only be used when the USAGE is set to "DesktopComponent".
+      </xs:documentation>
+    </xs:annotation>
+    <xs:attribute name="VALUE" type="OpenAsValue" use="optional" default="HTML">
+      <xs:annotation>
+        <xs:documentation>
+          Optional. String value specifying the content type of the Active Desktop item.
+          The VALUE attribute determines how the content will be hosted in the user's Active Desktop Desktop.htm file.
+        </xs:documentation>
+      </xs:annotation>
+    </xs:attribute>
+  </xs:complexType>
+
+  <xs:complexType name="WIDTH">
+    <xs:annotation>
+      <xs:documentation>
+        Indicates the width of the Microsoft Active Desktop item specified in the ITEM element.
+        Should only be used when the USAGE is set to "DesktopComponent".
+      </xs:documentation>
+    </xs:annotation>
+    <xs:attribute name="VALUE" type="xs:nonNegativeInteger" use="required">
+      <xs:annotation>
+        <xs:documentation>
+          Required. Numeric value specifying the width of the Active Desktop item.
+        </xs:documentation>
+      </xs:annotation>
+    </xs:attribute>
+  </xs:complexType>
+
+  <xs:group name="ActiveDesktopExtensions">
+    <xs:annotation>
+      <xs:documentation>
+        Those elements are extensions specific to channels used for Active Desktop items.
+        The VALUE attribute of the parent USAGE element must be set to "DesktopComponent" to use those elements.
+      </xs:documentation>
+    </xs:annotation>
+    <xs:all>
+      <xs:element name="CANRESIZE" type="CANRESIZE" minOccurs="0" />
+      <xs:element name="CANRESIZEX" type="CANRESIZEX" minOccurs="0" />
+      <xs:element name="CANRESIZEY" type="CANRESIZEY" minOccurs="0" />
+      <xs:element name="HEIGHT" type="HEIGHT" minOccurs="0" />
+      <xs:element name="OPENAS" type="OPENAS" minOccurs="0" />
+      <xs:element name="WIDTH" type="WIDTH" minOccurs="0" />
+    </xs:all>
+  </xs:group>
+
   <xs:simpleType name="sWhiteSpace">
     <xs:restriction base="xs:string">
       <xs:enumeration value="DEFAULT">
@@ -624,6 +776,7 @@ at <https://docs.microsoft.com/en-us/previous-versions/windows/internet-explorer
         Indicates how the parent element should be used.
       </xs:documentation>
     </xs:annotation>
+    <xs:group ref="ActiveDesktopExtensions" />
     <xs:attribute name="VALUE" type="sValue" use="required">
       <xs:annotation>
         <xs:documentation>
diff --git a/content/cdf.md b/content/cdf.md
index 430e288..8ed3f8c 100644
--- a/content/cdf.md
+++ b/content/cdf.md
@@ -25,6 +25,9 @@ I wrote my own XSD files to help me use this format in [ITSB][itsb]:
 * [W3C draft](./xsd/cdf-w3c.xsd)
 * [CDF 0.4](./xsd/cdf.xsd) (latest)
 
+The CDF 0.4 XSD includes the
+[CDF Extensions for Active Desktop Items][active-desktop-ext].
+
 ## Support
 
 CDF was supported by Internet Explorer 4 to 7, and no other software is known
@@ -61,11 +64,13 @@ tested and confirmed to be working with Internet Explorer 6 SP1 on Windows
 * [March 10th 1997 specification][docs-970314]
 * [March 21st 1997 specification][docs-970321]
 * [Latest documentation][docs] (CDF 0.4)
+* [Extensions for Active Desktop items][active-desktop-ext]
 * [Unofficial DTD][dtd]
 * [W3C draft][w3c]
 * Special Edition Using HTML 4, [Building Channels with CDF][building],
   Jerry Honeycutt
 
+[active-desktop-ext]: https://docs.microsoft.com/en-us/previous-versions/windows/internet-explorer/ie-developer/platform-apis/aa768141%28v=vs.85%29
 [building]: https://www.rigacci.org/docs/biblio/online/html4/ch30/ch30.htm
 [docs]: https://docs.microsoft.com/en-us/previous-versions/windows/internet-explorer/ie-developer/platform-apis/aa768139(v=vs.85)
 [docs-970314]: http://xml.coverpages.org/cdf970314.html