| --- | |
| title: Handling "Build Directory Not Writeable" Error in Next.js | |
| description: This document explains the "Build Directory Not Writeable" error in Next.js and provides a solution to resolve this issue. | |
| --- | |
| ## Why This Error Occurred | |
| The "Build Directory Not Writeable" error usually occurs when the file system does not permit writing to the designated directory. A common scenario for this error is when you initiate a [custom server](/docs/pages/guides/custom-server) in development mode on a production server. | |
| These production servers often disallow writing to the filesystem after your application is built, causing this error. | |
| ## Possible Ways to Fix It | |
| If you're deploying a custom server with a server file (let's assume it's named `server.js`), you should modify the scripts key in your `package.json` to the following: | |
| ```json filename="package.json" | |
| { | |
| "scripts": { | |
| "dev": "node server.js", | |
| "build": "next build", | |
| "start": "NODE_ENV=production node server.js" | |
| } | |
| } | |
| ``` | |
| Ensure that your custom server starts Next.js in production mode when `NODE_ENV` is set to `production`: | |
| ```js filename="server.js" | |
| const dev = process.env.NODE_ENV !== 'production' | |
| const app = next({ dev }) | |
| ``` | |
| ## Useful Links | |
| - [Custom Server documentation + examples](/docs/pages/guides/custom-server) - Learn more about how to effectively set up and manage an ejected server in Next.js. | |