prerendering.md
# Prerendering static pages
Angular Universal lets you prerender the pages of your application.
Prerendering is the process where a dynamic page is processed at build time generating static HTML.
## How to prerender a page
To prerender a static page make sure to add Server-Side Rendering (SSR) capabilities to your application.
For more information see the [universal guide](guide/universal).
Once SSR is added, run the following command:
<code-example format="shell" language="shell">
npm run prerender
</code-example>
### Build options for prerendering
When you add prerendering to your application, the following build options are available:
| Options | Details |
|:--- |:--- |
| `browserTarget` | Specify the target to build. |
| `serverTarget` | Specify the Server target to use for prerendering the application. |
| `routes` | Define an array of extra routes to prerender. |
| `guessRoutes` | Whether builder should extract routes and guess which paths to render. Defaults to `true`. |
| `routesFile` | Specify a file that contains a list of all routes to prerender, separated by newlines. This option is useful if you have a large number of routes. |
| `numProcesses` | Specify the number of CPUs to be used while running the prerendering command. |
### Prerendering dynamic routes
You can prerender dynamic routes.
An example of a dynamic route is `product/:id`, where `id` is dynamically provided.
To prerender dynamic routes, choose one from the following options:
* Provide extra routes in the command line
* Provide routes using a file
* Prerender specific routes
#### Provide extra routes in the command line
While running the prerender command, you can provide extra routes.
For example:
<code-example format="shell" language="shell">
ng run <app-name>:prerender --routes /product/1 /product/2
</code-example>
#### Providing extra routes using a file
You can provide routes using a file to create static pages.
This method is useful if you have a large number of routes to create. For example, product details for an e-commerce application, which might come from an external source, like a Database or Content Management System (CMS).
To provide routes using a file, use the `--routes-file` option with the name of a `.txt` file containing the routes.
For example, you could create this file by using a script to extract IDs from a database and save them to a `routes.txt` file:
<code-example language="none" header="routes.txt">
/products/1
/products/555
</code-example>
When your `.txt` file is ready, run the following command to prerender the static files with dynamic values:
<code-example format="shell" language="shell">
ng run <app-name>:prerender --routes-file routes.txt
</code-example>
#### Prerendering specific routes
You can also pass specific routes to the prerender command.
If you choose this option, make sure to turn off the `guessRoutes` option.
<code-example format="shell" language="shell">
ng run <app-name>:prerender --no-guess-routes --routes /product/1 /product/2
</code-example>
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@reviewed 2022-02-28