diff --git a/include/tidyenum.h b/include/tidyenum.h
index 3daee5b..543a82e 100644
--- a/include/tidyenum.h
+++ b/include/tidyenum.h
@@ -988,6 +988,7 @@ typedef enum
   TidyTag_OUTPUT,        /**< OUTPUT */
   TidyTag_PROGRESS,      /**< PROGRESS */
   TidyTag_SECTION,       /**< SECTION */
+  TidyTag_SLOT,          /**< SLOT */
   TidyTag_SOURCE,        /**< SOURCE */
   TidyTag_SUMMARY,       /**< SUMMARY */
   TidyTag_TEMPLATE,      /**< TEMPLATE */
@@ -1143,6 +1144,7 @@ typedef enum
   TidyAttr_SHOWGRIDX,              /**< SHOWGRIDX= */
   TidyAttr_SHOWGRIDY,              /**< SHOWGRIDY= */
   TidyAttr_SIZE,                   /**< SIZE= */
+  TidyAttr_SLOT,                   /**< SLOT= */
   TidyAttr_SPAN,                   /**< SPAN= */
   TidyAttr_SRC,                    /**< SRC= */
   TidyAttr_SRCSET,                 /**< SRCSET= (HTML5) */
diff --git a/src/attrdict.c b/src/attrdict.c
index 23322d1..c92d64e 100644
--- a/src/attrdict.c
+++ b/src/attrdict.c
@@ -95,6 +95,7 @@
   { TidyAttr_IS,                    xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|HT50|XH50 }, \
   { TidyAttr_LANG,                  xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|HT50|XH50 }, \
   { TidyAttr_ROLE,                  xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|HT50|XH50 }, \
+  { TidyAttr_SLOT,                  xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|HT50|XH50 }, \
   { TidyAttr_SPELLCHECK,            xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|HT50|XH50 }, \
   { TidyAttr_STYLE,                 xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|HT50|XH50 }, \
   { TidyAttr_TABINDEX,              xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|HT50|XH50 }, \
@@ -2880,6 +2881,17 @@ const AttrVersion TY_(W3CAttrsFor_SMALL)[] =
   { TidyAttr_UNKNOWN,               0                                                                          },
 };
 
+const AttrVersion TY_(W3CAttrsFor_SLOT)[] =
+{
+  INCLUDE_ARIA
+  INCLUDE_MICRODATA
+  { TidyAttr_NAME,                  xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|HT50|XH50 },
+  INCLUDE_CORE_ATTRIBS
+  INCLUDE_CORE_EVENTS
+  INCLUDE_RDFA
+  { TidyAttr_UNKNOWN,               0                                                                          },
+};
+
 const AttrVersion TY_(W3CAttrsFor_SOURCE)[] = 
 {
   INCLUDE_ARIA
diff --git a/src/attrdict.h b/src/attrdict.h
index 775ce40..4576300 100644
--- a/src/attrdict.h
+++ b/src/attrdict.h
@@ -142,6 +142,7 @@ extern const AttrVersion TY_(W3CAttrsFor_OUTPUT)[];
 extern const AttrVersion TY_(W3CAttrsFor_MENUITEM)[];
 extern const AttrVersion TY_(W3CAttrsFor_METER)[];
 extern const AttrVersion TY_(W3CAttrsFor_PROGRESS)[];
+extern const AttrVersion TY_(W3CAttrsFor_SLOT)[];
 extern const AttrVersion TY_(W3CAttrsFor_TEMPLATE)[];
 extern const AttrVersion TY_(W3CAttrsFor_TIME)[];
 extern const AttrVersion TY_(W3CAttrsFor_DATA)[];
diff --git a/src/attrs.c b/src/attrs.c
index 4231935..ff4f076 100644
--- a/src/attrs.c
+++ b/src/attrs.c
@@ -238,6 +238,7 @@ static const Attribute attribute_defs [] =
   { TidyAttr_SHOWGRIDX,               "showgridx",               CH_BOOL      }, /* TABLE Adobe golive*/
   { TidyAttr_SHOWGRIDY,               "showgridy",               CH_BOOL      }, /* TABLE Adobe golive*/
   { TidyAttr_SIZE,                    "size",                    CH_NUMBER    }, /* HR, FONT, BASEFONT, SELECT */
+  { TidyAttr_SLOT,                    "slot",                    CH_PCDATA    },
   { TidyAttr_SPAN,                    "span",                    CH_NUMBER    }, /* COL, COLGROUP */
   { TidyAttr_SRC,                     "src",                     CH_URL       }, /* IMG, FRAME, IFRAME */
   { TidyAttr_SRCSET,                  "srcset",                  CH_PCDATA    }, /* IMG (HTML5) */
diff --git a/src/attrs.h b/src/attrs.h
index befdcd1..c950acb 100644
--- a/src/attrs.h
+++ b/src/attrs.h
@@ -315,6 +315,7 @@ Bool TY_(AttributeIsMismatched)(Node* node, AttVal* attval, TidyDocImpl* doc);
 #define attrIsSHOWGRIDX(av)         AttrIsId( av, TidyAttr_SHOWGRIDX  )
 #define attrIsSHOWGRIDY(av)         AttrIsId( av, TidyAttr_SHOWGRIDY  )
 #define attrIsSIZE(av)              AttrIsId( av, TidyAttr_SIZE  )
+#define attrIsSLOT(av)              AttrIsId( av, TidyAttr_SLOT  )
 #define attrIsSPAN(av)              AttrIsId( av, TidyAttr_SPAN  )
 #define attrIsSRC(av)               AttrIsId( av, TidyAttr_SRC  )
 #define attrIsSTANDBY(av)           AttrIsId( av, TidyAttr_STANDBY  )
diff --git a/src/tags.c b/src/tags.c
index 34c08ff..70fb5ac 100644
--- a/src/tags.c
+++ b/src/tags.c
@@ -151,6 +151,7 @@ static CheckAttribs CheckHTML;
 #define VERS_ELEM_OUTPUT     (xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|HT50|XH50)
 #define VERS_ELEM_PROGRESS   (xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|HT50|XH50)
 #define VERS_ELEM_SECTION    (xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|HT50|XH50)
+#define VERS_ELEM_SLOT       (xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|HT50|XH50)
 #define VERS_ELEM_SOURCE     (xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|HT50|XH50)
 #define VERS_ELEM_SUMMARY    (xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|HT50|XH50)
 #define VERS_ELEM_TEMPLATE   (xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|HT50|XH50)
@@ -321,6 +322,7 @@ static Dict tag_defs[] =
   { TidyTag_OUTPUT,      "output",       VERS_ELEM_OUTPUT,      &TY_(W3CAttrsFor_OUTPUT)[0],      (CM_INLINE),                   TY_(ParseInline),    NULL           },
   { TidyTag_PROGRESS,    "progress",     VERS_ELEM_PROGRESS,    &TY_(W3CAttrsFor_PROGRESS)[0],    (CM_INLINE),                   TY_(ParseInline),    NULL           },
   { TidyTag_SECTION,     "section",      VERS_ELEM_SECTION,     &TY_(W3CAttrsFor_SECTION)[0],     (CM_BLOCK),                    TY_(ParseBlock),     NULL           },
+  { TidyTag_SLOT,        "slot",         VERS_ELEM_SLOT,        &TY_(W3CAttrsFor_SLOT)[0],        (CM_BLOCK|CM_INLINE|CM_MIXED), TY_(ParseBlock),     NULL           },
   { TidyTag_SOURCE,      "source",       VERS_ELEM_SOURCE,      &TY_(W3CAttrsFor_SOURCE)[0],      (CM_BLOCK|CM_INLINE|CM_EMPTY), TY_(ParseBlock),     NULL           },
   { TidyTag_SUMMARY,     "summary",      VERS_ELEM_SUMMARY,     &TY_(W3CAttrsFor_SUMMARY)[0],     (CM_BLOCK),                    TY_(ParseBlock),     NULL           }, /* Is. #895 */
   { TidyTag_TEMPLATE,    "template",     VERS_ELEM_TEMPLATE,    &TY_(W3CAttrsFor_TEMPLATE)[0],    (CM_BLOCK),                    TY_(ParseBlock),     NULL           },