diff --git a/site/Dockerfile b/site/Dockerfile
index c2a65122d9..0261a69521 100644
--- a/site/Dockerfile
+++ b/site/Dockerfile
@@ -1,3 +1,6 @@
+# IMPORTANT: Don't use this Dockerfile in your own Sapper projects without also looking at the .dockerignore file.
+# Without an appropriate .dockerignore, this Dockerfile will copy a large number of unneeded files into your image.
+
 FROM mhart/alpine-node:12
 
 # install dependencies