
Even with these improvements compared to the HTML `<img>` element, there's still a major problem. The 2000 by 2000 pixel image is sent to phones that render a smaller image.

With Next.js 10 we're also solving that problem. The `next/image` component will automatically generate smaller sizes through built-in Image Optimization.

```jsx
<img src="/profile-picture.jpg" width="400" height="400" alt="Profile Picture">
```

Built-in Image Optimization automatically serves the images in modern image formats like WebP, which is about 30% smaller than JPEG, if the browser supports it. It also allows Next.js to automatically adopt **future** image formats and serve them to browsers that support those formats.

```jsx
import Image from 'next/image'

<Image src="/profile-picture.jpg" width="400" height="400" alt="Profile Picture">
```

Image Optimization works with any image source. Even if images come from an external data source, like a CMS, they are optimized.

Instead of optimizing images at build time, Next.js 10 optimizes images on-demand, as users request them. Unlike static site generators and static-only solutions, your build times aren't increased, whether shipping 10 images or 10 million images.


Automatic Image Optimization


To get the best of both worlds, Next.js introduced **Incremental Static Generation**, updating static content after you have already built your site. By using the `fallback: true` option in `getStaticPaths`, you can **register new static pages at _runtime_**.

Next.js can statically pre-render an infinite number of pages this way, on-demand, no matter how large your dataset is.

Today, we are announcing the _general availability_ of **Incremental Static Re-generation**, which is a mechanism to update existing pages, by re-rendering them in the background as traffic comes in.

Inspired by [stale-while-revalidate](https://tools.ietf.org/html/rfc5861), background regeneration ensures traffic is served uninterruptedly, always from static storage, and the newly built page is pushed only after _it's done generating_.

```js showLineNumbers=true
export async function getStaticProps() {
  return {
    props: await getDataFromCMS(),
    // we will attempt to re-generate the page:
    // - when a request comes in
    // - at most once every second
    revalidate: 1,
  };
}
```

Unlike traditional SSR, Incremental Static Regeneration ensures you retain the benefits of static:

- No spikes in latency. Pages are served consistently fast.
- Pages never go offline. If the background page re-generation fails, the old page remains unaltered.
- Low database and backend load. Pages are re-computed at most once concurrently.

Both incremental features (adding pages and lazily updating them), as well as preview mode, are now stable and already fully supported by both next start and the Vercel edge platform out of the box.

## Customizable Base Path

Next.js projects are not always served from the root a domain. Sometimes you might want to host your Next.js project under a subpath like /docs so that the Next.js project only covers that subsection of the domain.

While this has been possible so far, it was at the expense of quite a bit of extra configuration. For example, adding the prefix to every single `<Link>` and making sure Next.js was serving the JavaScript bundles from the right path.

### Rewrites

To address this pain point, we're introducing a new configuration option. basePath allows you to easily host your Next.js project on a subpath of your domain.

To get started using basePath you can add it to `next.config.js`:

```js title=next.config.js
module.exports = {
  basePath: '/docs',
};
```

### Redirects

Using `next/link` in this way will result in the following HTML rendered to the web browser:

```html
<a href="/docs/documentation-page">Documentation page</a>
```


.css-aytm8m{color:var(--theme-ui-colors-heading,#111);-webkit-text-decoration:none;text-decoration:none;}.css-aytm8m:hover{color:var(--theme-ui-colors-primary,#06f);}Automatic Image Optimization

Stable Incremental Static Regeneration

Automatic Image Optimization