---
description: Configure how Next.js will dispose and keep in memory pages created in development.
# Configuring onDemandEntries
Next.js exposes some options that give you some control over how the server will dispose or keep in memory built pages in development.
To change the defaults, open `next.config.js` and add the `onDemandEntries` config:
```js
module.exports = {
onDemandEntries: {
// period (in ms) where the server will keep pages in the buffer
maxInactiveAge: 25 * 1000,
// number of pages that should be kept simultaneously without being disposed
pagesBufferLength: 2,
},
}
```