diff --git a/README.md b/README.md
index 56c5468..c25f8eb 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,9 @@
 # tiny-encrypt-java
 
-Tiny encrypt implemented by Java
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+Tiny encrypt implemented by Java
+
+Debug logging:
+
+```shell
+$ java -jar -Dcommons.log.debug=true tiny-encrypt.jar ...
+```
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