diff --git a/README.md b/README.md
index 9e68c9ec6..2380e4a9b 100644
--- a/README.md
+++ b/README.md
@@ -59,6 +59,15 @@ Misskey requires two domains called the primary domain and the secondary domain.
 
 **Ensure that the secondary domain is not a subdomain of the primary domain.**
 
+#### Dubdomains
+Misskey uses subdomains below:
+
+* **api**.<primary domain>
+* **auth**.<primary domain>
+* **about**.<primary domain>
+* **dev**.<primary domain>
+* **file**.<secondary domain>
+
 ### reCAPTCHA
 Please visit https://www.google.com/recaptcha/intro/ and generate keys.