diff --git a/README.md b/README.md
index 3f56980..0919ff6 100644
--- a/README.md
+++ b/README.md
@@ -35,3 +35,7 @@ parts of the URL in a GitHub secret.
 
 Not all services support the `title` option. It's optional and you can
 leave it out.
+
+> [!NOTE]
+> This action is only supported on Linux runners.
+> See <https://docs.github.com/en/actions/sharing-automations/creating-actions/about-custom-actions#types-of-actions>