next.js/errors/deploymentid-not-a-string.mdx

---
title: '`deploymentId` must be a string'
---

## Why This Error Occurred

The `deploymentId` option in your `next.config.js` must be a string value.

## Possible Ways to Fix It

Ensure your `deploymentId` is a string:

```js
// ✅ Correct
module.exports = {
  deploymentId: 'my-deployment-123',
}

// ✅ Using environment variables
module.exports = {
  deploymentId: process.env.GIT_HASH || 'default-id',
}

// ❌ Incorrect
module.exports = {
  deploymentId: 12345, // Must be a string, not a number
}
```

The `deploymentId` can be:

- A string: `deploymentId: 'my-deployment-123'`
- `undefined` (will use `NEXT_DEPLOYMENT_ID` environment variable if set)