diff --git a/README.md b/README.md
index faa5fd6..63fc23a 100644
--- a/README.md
+++ b/README.md
@@ -116,6 +116,8 @@ POSTGRES_DB=plasttrack
 POSTGRES_USER=plasttrack
 POSTGRES_PASSWORD=change-this-password
 FRONTEND_ORIGIN=http://SERVER_IP:5173
+FRONTEND_ORIGINS=http://SERVER_IP:5173,http://localhost:5173,http://127.0.0.1:5173
+BACKEND_PORT=8000
 VITE_API_BASE_URL=http://SERVER_IP:8000
 VITE_WS_URL=ws://SERVER_IP:8000/ws/dashboard
 VITE_ALLOWED_HOSTS=SERVER_IP,localhost,127.0.0.1
@@ -128,6 +130,8 @@ POSTGRES_DB=plasttrack
 POSTGRES_USER=plasttrack
 POSTGRES_PASSWORD=change-this-password
 FRONTEND_ORIGIN=https://plasttrack.example.com
+FRONTEND_ORIGINS=https://plasttrack.example.com
+BACKEND_PORT=8000
 VITE_API_BASE_URL=https://api.plasttrack.example.com
 VITE_WS_URL=wss://api.plasttrack.example.com/ws/dashboard
 VITE_ALLOWED_HOSTS=plasttrack.example.com
@@ -140,6 +144,22 @@ machine, not the Docker host.
 If Vite returns `Blocked request. This host is not allowed`, add the public
 frontend host to `VITE_ALLOWED_HOSTS` as a comma-separated value.
 
+If the backend host port conflicts with another service such as Portainer,
+change `BACKEND_PORT` instead of editing `docker-compose.yml`. For example:
+
+```env
+BACKEND_PORT=8001
+VITE_API_BASE_URL=http://SERVER_IP:8001
+VITE_WS_URL=ws://SERVER_IP:8001/ws/dashboard
+```
+
+If the browser shows a CORS error, make sure the exact frontend origin is in
+`FRONTEND_ORIGINS`. Example:
+
+```env
+FRONTEND_ORIGINS=https://plasttrack.sable.ynsdev.site
+```
+
 ### 3. Deploy
 
 Click `Deploy the stack`.
diff --git a/backend/app/config.py b/backend/app/config.py
index a09bdcf..a936d3e 100644
--- a/backend/app/config.py
+++ b/backend/app/config.py
@@ -18,7 +18,8 @@ class Settings(BaseSettings):
     mqtt_port: int = 1883
     mqtt_topic: str = "plasttrack/machines/+/events"
     mqtt_client_id: str = "plast-track-backend"
-    frontend_origin: str = "http://localhost:5173"
+    frontend_origin: str | None = None
+    frontend_origins: str = "http://localhost:5173,http://127.0.0.1:5173"
     downtime_check_interval_sec: int = 5
     database_startup_retries: int = 30
     database_startup_retry_delay_sec: float = 2.0
@@ -36,6 +37,13 @@ class Settings(BaseSettings):
             database=self.postgres_db,
         ).render_as_string(hide_password=False)
 
+    @property
+    def cors_allowed_origins(self) -> list[str]:
+        configured_origins = [origin.strip() for origin in self.frontend_origins.split(",") if origin.strip()]
+        if self.frontend_origin:
+            configured_origins.append(self.frontend_origin.strip())
+        return list(dict.fromkeys(configured_origins))
+
 
 @lru_cache
 def get_settings() -> Settings:
diff --git a/backend/app/main.py b/backend/app/main.py
index 2410703..b057120 100644
--- a/backend/app/main.py
+++ b/backend/app/main.py
@@ -148,7 +148,7 @@ async def lifespan(app: FastAPI):
 app = FastAPI(title=settings.app_name, lifespan=lifespan)
 app.add_middleware(
     CORSMiddleware,
-    allow_origins=[settings.frontend_origin, "http://localhost:5173", "http://127.0.0.1:5173"],
+    allow_origins=settings.cors_allowed_origins,
     allow_credentials=True,
     allow_methods=["*"],
     allow_headers=["*"],
diff --git a/docker-compose.yml b/docker-compose.yml
index a9970df..8685749 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -39,13 +39,14 @@ services:
       MQTT_PORT: 1883
       MQTT_TOPIC: plasttrack/machines/+/events
       FRONTEND_ORIGIN: ${FRONTEND_ORIGIN:-http://localhost:5173}
+      FRONTEND_ORIGINS: ${FRONTEND_ORIGINS:-http://localhost:5173,http://127.0.0.1:5173}
     depends_on:
       database:
         condition: service_healthy
       mqtt:
         condition: service_healthy
     ports:
-      - "8000:8000"
+      - "${BACKEND_PORT:-8000}:8000"
 
   edge-simulator:
     build: