diff --git a/README.md b/README.md
index d1fe49c..f509d8f 100644
--- a/README.md
+++ b/README.md
@@ -47,6 +47,12 @@ This directory contains comprehensive documentation for rewriting wttr.in in Zig
    - Based on location coordinates and timezone
    - Display in custom format output
 
+7. **Online GeoIP Fallback**
+   - When local GeoIP database lookup fails, fallback to online service
+   - Requires API key configuration
+   - Persistent cache for online lookup results
+   - Legacy system uses ip2location or similar service
+
 ## Documentation Files
 
 ### [TARGET_ARCHITECTURE.md](TARGET_ARCHITECTURE.md) ⭐ NEW