diff --git a/extension/compose.js b/extension/compose.js
new file mode 100644
index 0000000000000000000000000000000000000000..0b1bffca7b4fd99706b9ee4429adb10d59199d6d
--- /dev/null
+++ b/extension/compose.js
@@ -0,0 +1,13 @@
+// Modify the displayed message to clarify where safelinks are
+// inserted and to show the actual link targets.
+
+for (const link of document.links) {
+    if (isTangledLink(link.href)) {
+	link.href = untangleLink(link.href);
+    }
+}
+
+for (const node of getTextNodes(document)) {
+    node.textContent = untangleLink(node.textContent);
+}
+