diff --git a/autotests/folding/highlight.cpp.fold b/autotests/folding/highlight.cpp.fold
--- a/autotests/folding/highlight.cpp.fold
+++ b/autotests/folding/highlight.cpp.fold
@@ -428,6 +428,8 @@
 
 // Attributes
 
+int f(int i) [[expects: i > 0]] [[ensures audit x: x < 1]];
+
 [[noreturn]] void foo();
 [[deprecated]] void foo();
 [[deprecated("because")]] void foo();
diff --git a/autotests/html/highlight.cpp.html b/autotests/html/highlight.cpp.html
--- a/autotests/html/highlight.cpp.html
+++ b/autotests/html/highlight.cpp.html
@@ -434,6 +434,8 @@
 
 <span style="color:#898887;">// Attributes</span>
 
+<span style="color:#0057ae;">int</span> f(<span style="color:#0057ae;">int</span> i) [[<span style="color:#0057ae;font-style:italic;">expects</span>:<span style="color:#0057ae;font-style:italic;"> i </span>&gt;<span style="color:#0057ae;font-style:italic;"> </span><span style="color:#b08000;">0</span>]] [[<span style="color:#0057ae;font-style:italic;">ensures</span><span style="color:#0057ae;font-style:italic;"> </span><span style="color:#0057ae;font-style:italic;">audit</span><span style="color:#0057ae;font-style:italic;"> x</span>:<span style="color:#0057ae;font-style:italic;"> x </span>&lt;<span style="color:#0057ae;font-style:italic;"> </span><span style="color:#b08000;">1</span>]];
+
 [[<span style="color:#0057ae;font-style:italic;">noreturn</span>]] <span style="color:#0057ae;">void</span> foo();
 [[<span style="color:#0057ae;font-style:italic;">deprecated</span>]] <span style="color:#0057ae;">void</span> foo();
 [[<span style="color:#0057ae;font-style:italic;">deprecated</span>(<span style="color:#bf0303;">&quot;because&quot;</span>)]] <span style="color:#0057ae;">void</span> foo();
diff --git a/autotests/input/highlight.cpp b/autotests/input/highlight.cpp
--- a/autotests/input/highlight.cpp
+++ b/autotests/input/highlight.cpp
@@ -428,6 +428,8 @@
 
 // Attributes
 
+int f(int i) [[expects: i > 0]] [[ensures audit x: x < 1]];
+
 [[noreturn]] void foo();
 [[deprecated]] void foo();
 [[deprecated("because")]] void foo();
diff --git a/autotests/reference/highlight.cpp.ref b/autotests/reference/highlight.cpp.ref
--- a/autotests/reference/highlight.cpp.ref
+++ b/autotests/reference/highlight.cpp.ref
@@ -428,6 +428,8 @@
 <Normal Text></Normal Text><br/>
 <Comment>// Attributes</Comment><br/>
 <Normal Text></Normal Text><br/>
+<Data Type>int</Data Type><Normal Text> f</Normal Text><Symbol>(</Symbol><Data Type>int</Data Type><Normal Text> i</Normal Text><Symbol>)</Symbol><Normal Text> </Normal Text><Symbol>[[</Symbol><Standard Attribute>expects</Standard Attribute><Symbol>:</Symbol><Attribute> i </Attribute><Symbol>></Symbol><Attribute> </Attribute><Decimal>0</Decimal><Symbol>]]</Symbol><Normal Text> </Normal Text><Symbol>[[</Symbol><Standard Attribute>ensures</Standard Attribute><Attribute> </Attribute><Standard Attribute>audit</Standard Attribute><Attribute> x</Attribute><Symbol>:</Symbol><Attribute> x </Attribute><Symbol><</Symbol><Attribute> </Attribute><Decimal>1</Decimal><Symbol>]]</Symbol><Separator Symbol>;</Separator Symbol><br/>
+<Normal Text></Normal Text><br/>
 <Symbol>[[</Symbol><Standard Attribute>noreturn</Standard Attribute><Symbol>]]</Symbol><Normal Text> </Normal Text><Data Type>void</Data Type><Normal Text> foo</Normal Text><Symbol>()</Symbol><Separator Symbol>;</Separator Symbol><br/>
 <Symbol>[[</Symbol><Standard Attribute>deprecated</Standard Attribute><Symbol>]]</Symbol><Normal Text> </Normal Text><Data Type>void</Data Type><Normal Text> foo</Normal Text><Symbol>()</Symbol><Separator Symbol>;</Separator Symbol><br/>
 <Symbol>[[</Symbol><Standard Attribute>deprecated</Standard Attribute><Symbol>(</Symbol><String>"because"</String><Symbol>)]]</Symbol><Normal Text> </Normal Text><Data Type>void</Data Type><Normal Text> foo</Normal Text><Symbol>()</Symbol><Separator Symbol>;</Separator Symbol><br/>
diff --git a/data/syntax/isocpp.xml b/data/syntax/isocpp.xml
--- a/data/syntax/isocpp.xml
+++ b/data/syntax/isocpp.xml
@@ -22,7 +22,7 @@
 <language
     name="ISO C++"
     section="Sources"
-    version="14"
+    version="15"
     kateversion="5.0"
     indenter="cstyle"
     style="C++"
@@ -38,6 +38,7 @@
     http://kde-files.org/content/show.php?content=90660
   -->
   <highlighting>
+    <!-- https://en.cppreference.com/w/cpp/keyword -->
     <list name="controlflow">
       <item>break</item>
       <item>case</item>
@@ -55,22 +56,21 @@
       <item>try</item>
       <item>while</item>
     </list>
+
     <list name="keywords">
       <item>alignof</item>
       <item>alignas</item>
       <item>asm</item>
       <item>auto</item>
       <item>class</item>
-      <item>concept</item> <!-- C++20 -->
-      <item>requires</item> <!-- C++20 -->
+      <item>consteval</item> <!-- C++20 -->
       <item>constexpr</item>
       <item>const_cast</item>
       <item>decltype</item>
       <item>delete</item>
       <item>dynamic_cast</item>
       <item>enum</item>
       <item>explicit</item>
-      <item>export</item> <!-- Unused but reserved for future use -->
       <item>false</item>
       <item>final</item> <!-- According N3272 -->
       <item>friend</item>
@@ -110,20 +110,26 @@
       <item>or_eq</item>
       <item>xor</item>
       <item>xor_eq</item>
+      <!-- Contract -->
+      <item>concept</item>
+      <item>requires</item>
       <!-- TM TS -->
-      <!-- <list>atomic_cancel</list>
-      <list>atomic_commit</list>
-      <list>atomic_noexcept</list>
-      <list>synchronized</list>
-      <list>transaction_safe</list>
-      <list>transaction_safe_dynamic</list> -->
-      <!-- module TS -->
-      <!-- <list>import</list>
-      <list>module</list> -->
-      <!-- coroutine TS -->
-      <!-- <list>co_await</list>
-      <list>co_return</list>
-      <list>co_yield</list> -->
+      <!-- <item>atomic_cancel</item>
+      <item>atomic_commit</item>
+      <item>atomic_noexcept</item>
+      <item>synchronized</item>
+      <item>transaction_safe</item>
+      <item>transaction_safe_dynamic</item> -->
+      <!-- module -->
+      <item>import</item>
+      <item>module</item>
+      <item>export</item> <!-- Unused but reserved, keyword since c++20 -->
+      <!-- coroutine -->
+      <item>co_await</item>
+      <item>co_return</item>
+      <item>co_yield</item>
+      <!-- reflexion TS -->
+      <!-- <item>reflexpr</item> -->
     </list>
     <!-- This keyword may appear in InternalsNS context. For example in code:
       details::some_class::template some_templated_static();
@@ -152,17 +158,31 @@
       <!-- TM TS -->
       <!-- <item>optimize_for_synchronized</item> -->
     </list>
+    <list name="contractAttributes">
+      <!-- C++20 -->
+      <item>assert</item>
+      <item>ensures</item>
+      <item>expects</item>
+    </list>
+    <list name="contractLevel">
+      <!-- C++20 -->
+      <item>default</item>
+      <item>audit</item>
+      <item>axiom</item>
+    </list>
     <!-- This keyword may appear in Attribute context. For example in code:
     [[using CC: opt(1), debug]]
     and it should be displayed as keyword, not like part of attribute...
     -->
     <list name="using">
       <item>using</item>
     </list>
 
+    <!-- https://en.cppreference.com/w/cpp/keyword -->
     <list name="types">
       <item>bool</item>
       <item>char</item>
+      <item>char8_t</item> <!-- C++20 -->
       <item>char16_t</item>
       <item>char32_t</item>
       <item>double</item>
@@ -216,7 +236,7 @@
       <item>const</item>
       <item>extern</item>
       <item>mutable</item>
-      <item>register</item>
+      <item>register</item> <!-- The keyword is unused and reserved (c++17) -->
       <item>static</item>
       <item>thread_local</item>
       <item>volatile</item>
@@ -239,7 +259,10 @@
       <item>__func__</item>
       <item>assert</item>
       <item>_Pragma</item>
+      <!-- C++17 -->
       <item>__has_include</item>
+      <!-- C++20 -->
+      <item>__has_cpp_attribute</item>
     </list>
     <list name="InMacro">
       <item>__VA_ARGS__</item>
@@ -505,7 +528,9 @@
 
 
       <context name="Attribute" attribute="Attribute" lineEndContext="#stay">
+        <DetectSpaces/>
         <keyword attribute="Standard Attribute" context="#stay" String="attributes" />
+        <keyword attribute="Standard Attribute" context="Contract Attribute" String="contractAttributes" />
         <Detect2Chars attribute="Symbol" context="#pop" char="]" char1="]" />
         <DetectChar attribute="Separator Symbol" context="#stay" char="," />
         <AnyChar attribute="Symbol" context="#stay" String="&punctuators;" />
@@ -518,6 +543,11 @@
         <DetectIdentifier />
       </context>
 
+      <context name="Contract Attribute" attribute="Attribute" lineEndContext="#pop" fallthrough="true" fallthroughContext="#pop">
+        <DetectSpaces/>
+        <keyword attribute="Standard Attribute" context="#pop" String="contractLevel" />
+      </context>
+
       <context name="Attribute In PP" attribute="Attribute" lineEndContext="#pop">
         <IncludeRules context="InPreprocessor" />
         <IncludeRules context="Attribute" />