Defining routes by using predefined paths is not always enough for complex applications. In Next.js you can add brackets to a page (`[param]`) to create a dynamic route (a.k.a. url slugs, pretty urls, and others).
Consider the following page `pages/post/[pid].js`:
```jsx
import { useRouter } from 'next/router'
const Post = () => {
const router = useRouter()
const { pid } = router.query
return <p>Post: {pid}</p>
}
export default Post
```
Any route like `/post/1`, `/post/abc`, etc. will be matched by `pages/post/[pid].js`. The matched path parameter will be sent as a query parameter to the page, and it will be merged with the other query parameters.
For example, the route `/post/abc` will have the following `query` object:
```json
{ "pid": "abc" }
```
Similarly, the route `/post/abc?foo=bar` will have the following `query` object:
```json
{ "foo": "bar", "pid": "abc" }
```
However, route parameters will override query parameters with the same name. For example, the route `/post/abc?pid=123` will have the following `query` object:
```json
{ "pid": "abc" }
```
Multiple dynamic route segments work the same way. The page `pages/post/[pid]/[comment].js` will match the route `/post/abc/a-comment` and its `query` object will be:
```json
{ "pid": "abc", "comment": "a-comment" }
```
Client-side navigations to a dynamic route can be handled with [`next/link`](/docs/api-reference/next/link.md#dynamic-routes).
Matched parameters will be sent as a query parameter (`slug` in the example) to the page, and it will always be an array, so, the path `/post/a` will have the following `query` object:
> A good example of catch all routes is the Next.js docs, a single page called [pages/docs/[...slug].js](https://github.com/zeit/next-site/blob/master/pages/docs/%5B...slug%5D.js) takes care of all the docs you're currently looking at.
- Pages that are statically optimized by [Automatic Static Optimization](/docs/advanced-features/automatic-static-optimization.md) will be hydrated without their route parameters provided, i.e `query` will be an empty object (`{}`).
After hydration, Next.js will trigger an update to your application to provide the route parameters in the `query` object.