diff --git a/README.md b/README.md
index 4a93fdc..6d215af 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,10 @@
+> **Retired — 28 October 2026**
+>
+> KarlDNS has been retired. The public service at **karldns.de** is no longer available,
+> and existing KarlDNS hostnames will no longer be updated. This repository is retained
+> as a read-only source archive. The setup instructions below are historical and do not
+> describe a currently operated or supported service. Please use another DDNS provider.
+
 # KarlDNS
 
 **Self-hosted Dynamic DNS (DynDNS / DDNS) for FRITZ!Box, OpenWrt, pfSense, OPNsense, UniFi, MikroTik, Linux cron jobs, and any router that can call a custom DDNS update URL.**