fix: nextjs only reads .env files when using NEXT_PUBLIC_ in front of variables + definition of right .env of root

.env

@@ -3,5 +3,5 @@ NODE_ENV=development
 HOSTNAME=0.0.0.0
 FRONTEND_PORT=3000
 BACKEND_PORT=4000
-BACKEND=http://localhost:4000
+NEXT_PUBLIC_BACKEND_URL=http://localhost:4000
 CORS_ALLOWED_ORIGIN=http://localhost:3000

docker-compose.yaml

@@ -9,7 +9,7 @@ services:
       - NODE_ENV=${NODE_ENV}
       - HOSTNAME=${HOSTNAME}
       - PORT=${FRONTEND_PORT}
-      - BACKEND_URL=${BACKEND}
+      - NEXT_PUBLIC_BACKEND_URL=${NEXT_PUBLIC_BACKEND_URL}
     ports:
       - "${FRONTEND_PORT}:3000"
     restart: unless-stopped

frontend/next.config.ts

@@ -1,9 +1,12 @@
 import type { NextConfig } from "next";
+import dotenv from "dotenv";
+
+dotenv.config({ path: "../.env" });
 
 const nextConfig: NextConfig = {
   output: "standalone",
   env: {
-    backend_url: process.env.BACKEND_URL || "http://localhost:4000",
+    backend_url: process.env.NEXT_PUBLIC_BACKEND_URL,
   },
 };
 

frontend/package-lock.json

@@ -10,6 +10,7 @@
       "dependencies": {
         "class-variance-authority": "^0.7.1",
         "clsx": "^2.1.1",
+        "dotenv": "^16.4.7",
         "libreoffice-convert": "^1.6.0",
         "lucide-react": "^0.475.0",
         "next": "15.1.6",
@@ -1983,6 +1984,18 @@
         "node": ">=0.10.0"
       }
     },
+    "node_modules/dotenv": {
+      "version": "16.4.7",
+      "resolved": "https://registry.npmjs.org/dotenv/-/dotenv-16.4.7.tgz",
+      "integrity": "sha512-47qPchRCykZC03FhkYAhrvwU4xDBFIj1QPqaarj6mdM/hgUzfPHcpkHJOn3mJAufFeeAxAzeGsr5X0M4k6fLZQ==",
+      "license": "BSD-2-Clause",
+      "engines": {
+        "node": ">=12"
+      },
+      "funding": {
+        "url": "https://dotenvx.com"
+      }
+    },
     "node_modules/dunder-proto": {
       "version": "1.0.1",
       "resolved": "https://registry.npmjs.org/dunder-proto/-/dunder-proto-1.0.1.tgz",

frontend/package.json

@@ -11,6 +11,7 @@
   "dependencies": {
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
+    "dotenv": "^16.4.7",
     "libreoffice-convert": "^1.6.0",
     "lucide-react": "^0.475.0",
     "next": "15.1.6",