diff --git a/doc/go1.21.html b/doc/go1.21.html
index 1c7fb9ec5c..39787e51f1 100644
--- a/doc/go1.21.html
+++ b/doc/go1.21.html
@@ -139,6 +139,22 @@ Do not send CLs removing the interior tags from such phrases.
 
 <h2 id="ports">Ports</h2>
 
+<h3 id="darwin">Darwin</h3>
+
+<p><!-- go.dev/issue/57125 -->
+  As <a href="go1.20#darwin">announced</a> in the Go 1.20 release notes,
+  Go 1.21 requires macOS 10.15 Catalina or later;
+  support for previous versions has been discontinued.
+</p>
+
+<h3 id="windows">Windows</h3>
+
+<p><!-- go.dev/issue/57003, go.dev/issue/57004 -->
+  As <a href="go1.20#windows">announced</a> in the Go 1.20 release notes,
+  Go 1.21 requires at least Windows 10 or Windows Server 2016;
+  support for previous versions has been discontinued.
+</p>
+
 <!-- CL 470695 -->
 <p>
   <!-- cmd/dist: default to GOARM=7 on all non-arm systems -->