diff --git a/create-nginx-map.py b/create-nginx-map.py
index 75bb265..34af038 100644
--- a/create-nginx-map.py
+++ b/create-nginx-map.py
@@ -1,5 +1,6 @@
 from typing import NamedTuple
 import re
+from io import StringIO
 import sys
 import tomllib
 from pathlib import Path
@@ -103,12 +104,21 @@ def main():
     for route in routes:
         grouped_routes[route.hostname, route.destination].add(route.name)
 
-    with args.output.open("w", buffering=1024 * 1024) as f:
-        for (hostname, destination), names in sorted(grouped_routes.items()):
-            print(f"{hostname}\t{destination};  # {', '.join(names)}", file=f)
-
     print("Found", len(routes), "routes, grouped into", len(grouped_routes), "groups")
 
+    output = StringIO()
+    for (hostname, destination), names in sorted(grouped_routes.items()):
+        output.write(f"{hostname}\t{destination};  # {', '.join(names)}\n")
+
+    if args.output.is_file():
+        current_output = args.output.read_text()
+
+        if current_output == output.getvalue():
+            print("Output identical - aborting")
+            return
+
+    args.output.write_text(output.getvalue())
+
     if args.reload:
         print("Reloading nginx")
         subprocess.check_call(