diff --git a/.env.example b/.env.example
index 9c932365..68c958e4 100644
--- a/.env.example
+++ b/.env.example
@@ -14,7 +14,7 @@ UVICORN_PORT = 8000
 
 # XRAY_JSON = "xray_config.json"
 # XRAY_SUBSCRIPTION_URL_PREFIX = "https://example.com"
-# XRAY_SUBSCRIPTION_PATH = sub
+# XRAY_SUBSCRIPTION_PATH = "sub"
 # XRAY_EXECUTABLE_PATH = "/usr/local/bin/xray"
 # XRAY_ASSETS_PATH = "/usr/local/share/xray"
 # XRAY_EXCLUDE_INBOUND_TAGS = "INBOUND_X INBOUND_Y"
@@ -37,8 +37,12 @@ UVICORN_PORT = 8000
 # SINGBOX_SUBSCRIPTION_TEMPLATE="singbox/default.json"
 # MUX_TEMPLATE="mux/default.json"
 
-## Enable JSON support for compatible clients to use mux, fragment, etc. Default is null, meaning false.
-# USE_CUSTOM_JSON_DEFAULT="True" 
+## Enable JSON config for compatible clients to use mux, fragment, etc. Default False.
+# USE_CUSTOM_JSON_DEFAULT=True
+## Your preferred config type for different clients
+## If USE_CUSTOM_JSON_DEFAULT is set True, all following programs will use the JSON config
+# USE_CUSTOM_JSON_FOR_V2RAYN=False
+# USE_CUSTOM_JSON_FOR_V2RAYNG=True
 
 ## Set headers for subscription
 # SUB_PROFILE_TITLE = "Susbcription"
@@ -55,8 +59,8 @@ UVICORN_PORT = 8000
 # ONHOLD_STATUS_TEXT = "On-Hold"
 
 ### for developers
-# DOCS=true
-# DEBUG=true
+# DOCS=True
+# DEBUG=True
 
 # If You Want To Send Webhook To Multiple Server Add Multi Address
 # WEBHOOK_ADDRESS = "http://127.0.0.1:9000/,http://127.0.0.1:9001/"
diff --git a/app/views/subscription.py b/app/views/subscription.py
index 8c1d21d9..31e021fd 100644
--- a/app/views/subscription.py
+++ b/app/views/subscription.py
@@ -17,7 +17,9 @@
     SUB_UPDATE_INTERVAL,
     SUBSCRIPTION_PAGE_TEMPLATE,
     XRAY_SUBSCRIPTION_PATH,
-    USE_CUSTOM_JSON_DEFAULT
+    USE_CUSTOM_JSON_DEFAULT,
+    USE_CUSTOM_JSON_FOR_V2RAYN,
+    USE_CUSTOM_JSON_FOR_V2RAYNG
 )
 
 
@@ -92,14 +94,25 @@ def get_subscription_user_info(user: UserResponse) -> dict:
         conf = generate_subscription(user=user, config_format="outline", as_base64=False)
         return Response(content=conf, media_type="application/json", headers=response_headers)
 
+    elif re.match('^v2rayN/(\d+\.\d+)', user_agent):
+        version_str = re.match('^v2rayN/(\d+\.\d+)', user_agent).group(1)
+        if LooseVersion(version_str) >= LooseVersion("6.40") and \
+                (USE_CUSTOM_JSON_DEFAULT or USE_CUSTOM_JSON_FOR_V2RAYN):
+            conf = generate_subscription(user=user, config_format="v2ray-json", as_base64=False)
+            return Response(content=conf, media_type="application/json", headers=response_headers)
+        else:
+            conf = generate_subscription(user=user, config_format="v2ray", as_base64=True)
+            return Response(content=conf, media_type="text/plain", headers=response_headers)
+
     elif re.match('^v2rayNG/(\d+\.\d+\.\d+)', user_agent):
         version_str = re.match('^v2rayNG/(\d+\.\d+\.\d+)', user_agent).group(1)
-        if LooseVersion(version_str) >= LooseVersion("1.8.16") and USE_CUSTOM_JSON_DEFAULT:
+        if LooseVersion(version_str) >= LooseVersion("1.8.16") and \
+                (USE_CUSTOM_JSON_DEFAULT or USE_CUSTOM_JSON_FOR_V2RAYNG):
             conf = generate_subscription(user=user, config_format="v2ray-json", as_base64=False)
             return Response(content=conf, media_type="application/json", headers=response_headers)
         else:
             conf = generate_subscription(user=user, config_format="v2ray", as_base64=True)
-            return Response(content=conf, media_type="application/json", headers=response_headers)
+            return Response(content=conf, media_type="text/plain", headers=response_headers)
 
     else:
         conf = generate_subscription(user=user, config_format="v2ray", as_base64=True)
@@ -141,7 +154,7 @@ def user_get_usage(token: str,
         return Response(status_code=204)
 
     if start is None:
-        start_date = datetime.fromtimestamp(datetime.utcnow().timestamp() - 30 * 24 * 3600)
+        start_date = datetime.utcfromtimestamp(datetime.utcnow().timestamp() - 30 * 24 * 3600)
     else:
         start_date = datetime.fromisoformat(start)
 
diff --git a/config.py b/config.py
index ec415b1a..a75cb230 100755
--- a/config.py
+++ b/config.py
@@ -50,7 +50,10 @@
 SINGBOX_SUBSCRIPTION_TEMPLATE = config("SINGBOX_SUBSCRIPTION_TEMPLATE", default="singbox/default.json")
 MUX_TEMPLATE = config("MUX_TEMPLATE", default="mux/default.json")
 V2RAY_SUBSCRIPTION_TEMPLATE = config("V2RAY_SUBSCRIPTION_TEMPLATE", default="v2ray/default.json")
-USE_CUSTOM_JSON_DEFAULT = config("USE_CUSTOM_JSON_DEFAULT", default="")
+
+USE_CUSTOM_JSON_DEFAULT = config("USE_CUSTOM_JSON_DEFAULT", default=False, cast=bool)
+USE_CUSTOM_JSON_FOR_V2RAYN = config("USE_CUSTOM_JSON_FOR_V2RAYN", default=False, cast=bool)
+USE_CUSTOM_JSON_FOR_V2RAYNG = config("USE_CUSTOM_JSON_FOR_V2RAYNG", default=False, cast=bool)
 
 ACTIVE_STATUS_TEXT = config("ACTIVE_STATUS_TEXT", default="Active")
 EXPIRED_STATUS_TEXT = config("EXPIRED_STATUS_TEXT", default="Expired")