diff --git a/fetch-proxy/preview.py b/fetch-proxy/preview.py
--- a/fetch-proxy/preview.py
+++ b/fetch-proxy/preview.py
@@ -1,4 +1,6 @@
 """Lab URL preview for fetch-proxy. Synthetic."""
 
+import urllib.request
+
 def preview(url):
-    return url
+    return urllib.request.urlopen(url).read()