angular-cn/aio/content/guide/deployment.md

# Deployment

When you are ready to deploy your Angular application to a remote server, you have various options for deployment.

{@a dev-deploy}
{@a copy-files}


## Simple deployment options

Before fully deploying your application, you can test the process, build configuration, and deployed behavior by using one of these interim techniques

### Building and serving from disk

During development, you typically use the `ng serve` command to build, watch, and serve the application from local memory, using [webpack-dev-server](https://webpack.js.org/guides/development/#webpack-dev-server).
When you are ready to deploy, however, you must use the `ng build` command to build the app and deploy the build artifacts elsewhere.

Both `ng build` and `ng serve` clear the output folder before they build the project, but only the `ng build` command writes the generated build artifacts to the output folder.

<div class="alert is-helpful">

The output folder is  `dist/project-name/` by default.
To output to a different folder, change the `outputPath` in `angular.json`.

</div>

As you near the end of the development process, serving the contents of your output folder from a local web server can give you a better idea of how your application will behave when it is deployed to a remote server.
You will need two terminals to get the live-reload experience.

* On the first terminal, run the [`ng build` command](cli/build) in *watch* mode to compile the application to the `dist` folder.

  <code-example language="none" class="code-shell">
   ng build --watch
  </code-example>

  Like the `ng serve` command, this regenerates output files when source files change.

* On the second terminal, install a web server (such as [lite-server](https://github.com/johnpapa/lite-server)), and run it against the output folder. For example:

  <code-example language="none" class="code-shell">
   lite-server --baseDir="dist"
  </code-example>

   The server will automatically reload your browser when new files are output.

<div class="alert is-critical">

This method is for development and testing only, and is not a supported or secure way of deploying an application.

</div>

### Basic deployment to a remote server

For the simplest deployment, create a production build and copy the output directory to a web server.

1. Start with the production build:

  <code-example language="none" class="code-shell">
    ng build --prod
  </code-example>


2. Copy _everything_ within the output folder (`dist/` by default) to a folder on the server.

3. Configure the server to redirect requests for missing files to `index.html`.
Learn more about server-side redirects [below](#fallback).

This is the simplest production-ready deployment of your application.

{@a deploy-to-github}

### Deploy to GitHub pages

Another simple way to deploy your Angular app is to use [GitHub Pages](https://help.github.com/articles/what-is-github-pages/).

1. You need to [create a GitHub account](https://github.com/join) if you don't have one, and then [create a repository](https://help.github.com/articles/create-a-repo/) for your project.
Make a note of the user name and project name in GitHub.

1. Build your project using Github project name, with the Angular CLI command [`ng build`](cli/build) and the options shown here:
   <code-example language="none" class="code-shell">
     ng build --prod --output-path docs --base-href /<project_name>/
    </code-example>

1. When the build is complete, make a copy of `docs/index.html` and name it `docs/404.html`.

1. Commit your changes and push.

1. On the GitHub project page, configure it to [publish from the docs folder](https://help.github.com/articles/configuring-a-publishing-source-for-github-pages/#publishing-your-github-pages-site-from-a-docs-folder-on-your-master-branch).

You can see your deployed page at `https://<user_name>.github.io/<project_name>/`.

<div class="alert is-helpful">

Check out [angular-cli-ghpages](https://github.com/angular-buch/angular-cli-ghpages), a full featured package that does all this for you and has extra functionality.

</div>

<hr>

{@a server-configuration}

## Server configuration

This section covers changes you may have make to the server or to files deployed to the server.

{@a fallback}

### Routed apps must fallback to `index.html`

Angular apps are perfect candidates for serving with a simple static HTML server.
You don't need a server-side engine to dynamically compose application pages because
Angular does that on the client-side.

If the app uses the Angular router, you must configure the server
to return the application's host page (`index.html`) when asked for a file that it does not have.

{@a deep-link}

A routed application should support "deep links".
A _deep link_ is a URL that specifies a path to a component inside the app.
For example, `http://www.mysite.com/heroes/42` is a _deep link_ to the hero detail page
that displays the hero with `id: 42`.

There is no issue when the user navigates to that URL from within a running client.
The Angular router interprets the URL and routes to that page and hero.

But clicking a link in an email, entering it in the browser address bar,
or merely refreshing the browser while on the hero detail page &mdash;
all of these actions are handled by the browser itself, _outside_ the running application.
The browser makes a direct request to the server for that URL, bypassing the router.

A static server routinely returns `index.html` when it receives a request for `http://www.mysite.com/`.
But it rejects `http://www.mysite.com/heroes/42` and returns a `404 - Not Found` error *unless* it is
configured to return `index.html` instead.

#### Fallback configuration examples

There is no single configuration that works for every server.
The following sections describe configurations for some of the most popular servers.
The list is by no means exhaustive, but should provide you with a good starting point.

* [Apache](https://httpd.apache.org/): add a
[rewrite rule](http://httpd.apache.org/docs/current/mod/mod_rewrite.html) to the `.htaccess` file as shown
  (https://ngmilk.rocks/2015/03/09/angularjs-html5-mode-or-pretty-urls-on-apache-using-htaccess/):

  <code-example format=".">
    RewriteEngine On
    &#35 If an existing asset or directory is requested go to it as it is
    RewriteCond %{DOCUMENT_ROOT}%{REQUEST_URI} -f [OR]
    RewriteCond %{DOCUMENT_ROOT}%{REQUEST_URI} -d
    RewriteRule ^ - [L]

    &#35 If the requested resource doesn't exist, use index.html
    RewriteRule ^ /index.html
  </code-example>


* [Nginx](http://nginx.org/): use `try_files`, as described in
[Front Controller Pattern Web Apps](https://www.nginx.com/resources/wiki/start/topics/tutorials/config_pitfalls/#front-controller-pattern-web-apps),
modified to serve `index.html`:

  <code-example format=".">
    try_files $uri $uri/ /index.html;
  </code-example>


* [IIS](https://www.iis.net/): add a rewrite rule to `web.config`, similar to the one shown
[here](http://stackoverflow.com/a/26152011/2116927):

  <code-example format='.'>
    &lt;system.webServer&gt;
      &lt;rewrite&gt;
        &lt;rules&gt;
          &lt;rule name="Angular Routes" stopProcessing="true"&gt;
            &lt;match url=".*" /&gt;
            &lt;conditions logicalGrouping="MatchAll"&gt;
              &lt;add input="{REQUEST_FILENAME}" matchType="IsFile" negate="true" /&gt;
              &lt;add input="{REQUEST_FILENAME}" matchType="IsDirectory" negate="true" /&gt;
            &lt;/conditions&gt;
            &lt;action type="Rewrite" url="/index.html" /&gt;
          &lt;/rule&gt;
        &lt;/rules&gt;
      &lt;/rewrite&gt;
    &lt;/system.webServer&gt;

  </code-example>


* [GitHub Pages](https://pages.github.com/): you can't
[directly configure](https://github.com/isaacs/github/issues/408)
the GitHub Pages server, but you can add a 404 page.
Copy `index.html` into `404.html`.
It will still be served as the 404 response, but the browser will process that page and load the app properly.
It's also a good idea to
[serve from `docs/` on master](https://help.github.com/articles/configuring-a-publishing-source-for-github-pages/#publishing-your-github-pages-site-from-a-docs-folder-on-your-master-branch)
and to
[create a `.nojekyll` file](https://www.bennadel.com/blog/3181-including-node-modules-and-vendors-folders-in-your-github-pages-site.htm)


* [Firebase hosting](https://firebase.google.com/docs/hosting/): add a
[rewrite rule](https://firebase.google.com/docs/hosting/url-redirects-rewrites#section-rewrites).

  <code-example format=".">
    "rewrites": [ {
      "source": "**",
      "destination": "/index.html"
    } ]

  </code-example>

{@a cors}

### Requesting services from a different server (CORS)

Angular developers may encounter a
<a href="https://en.wikipedia.org/wiki/Cross-origin_resource_sharing" title="Cross-origin resource sharing">
<i>cross-origin resource sharing</i></a> error when making a service request (typically a data service request)
to a server other than the application's own host server.
Browsers forbid such requests unless the server permits them explicitly.

There isn't anything the client application can do about these errors.
The server must be configured to accept the application's requests.
Read about how to enable CORS for specific servers at
<a href="http://enable-cors.org/server.html" title="Enabling CORS server">enable-cors.org</a>.

<hr>

{@a optimize}

## Production optimizations

The `--prod` _meta-flag_ engages the following build optimization features.

* [Ahead-of-Time (AOT) Compilation](guide/aot-compiler): pre-compiles Angular component templates.
* [Production mode](#enable-prod-mode): deploys the production environment which enables _production mode_.
* Bundling: concatenates your many application and library files into a few bundles.
* Minification: removes excess whitespace, comments, and optional tokens.
* Uglification: rewrites code to use short, cryptic variable and function names.
* Dead code elimination: removes unreferenced modules and much unused code.

See [`ng build`](cli/build) for more about CLI build options and what they do.


{@a enable-prod-mode}

### Enable runtime production mode

In addition to build optimizations, Angular also has a runtime production mode. Angular apps run in development mode by default, as you can see by the following message on the browser console:

<code-example format="nocode">
  Angular is running in the development mode. Call enableProdMode() to enable the production mode.
</code-example>

Switching to _production mode_ makes it run faster by disabling development specific checks such as the dual change detection cycles.

When you enable production builds via `--prod` command line flag, the runtime production mode is enabled as well.

{@a lazy-loading}

### Lazy loading

You can dramatically reduce launch time by only loading the application modules that
absolutely must be present when the app starts.

Configure the Angular Router to defer loading of all other modules (and their associated code), either by
[waiting until the app has launched](guide/router#preloading  "Preloading")
or by [_lazy loading_](guide/router#asynchronous-routing "Lazy loading")
them on demand.

<div class="alert is-helpful>

#### Don't eagerly import something from a lazy-loaded module

If you mean to lazy-load a module, be careful not import it
in a file that's eagerly loaded when the app starts (such as the root `AppModule`).
If you do that, the module will be loaded immediately.

The bundling configuration must take lazy loading into consideration.
Because lazy-loaded modules aren't imported in JavaScript, bundlers exclude them by default.
Bundlers don't know about the router configuration and can't create separate bundles for lazy-loaded modules.
You would have to create these bundles manually.

The CLI runs the
[Angular Ahead-of-Time Webpack Plugin](https://github.com/angular/angular-cli/tree/master/packages/%40ngtools/webpack)
which automatically recognizes lazy-loaded `NgModules` and creates separate bundles for them.

</div>

{@a measure}

### Measure performance

You can make better decisions about what to optimize and how when you have a clear and accurate understanding of
what's making the application slow.
The cause may not be what you think it is.
You can waste a lot of time and money optimizing something that has no tangible benefit or even makes the app slower.
You should measure the app's actual behavior when running in the environments that are important to you.

The
<a href="https://developers.google.com/web/tools/chrome-devtools/network-performance/understanding-resource-timing" title="Chrome DevTools Network Performance">
Chrome DevTools Network Performance page</a> is a good place to start learning about measuring performance.

The [WebPageTest](https://www.webpagetest.org/) tool is another good choice
that can also help verify that your deployment was successful.

{@a inspect-bundle}

### Inspect the bundles

The <a href="https://github.com/danvk/source-map-explorer/blob/master/README.md">source-map-explorer</a>
tool is a great way to inspect the generated JavaScript bundles after a production build.

Install `source-map-explorer`:

<code-example language="none" class="code-shell">
  npm install source-map-explorer --save-dev
</code-example>

Build your app for production _including the source maps_

<code-example language="none" class="code-shell">
  ng build --prod --source-map
</code-example>

List the generated bundles in the `dist/` folder.

<code-example language="none" class="code-shell">
  ls dist/*.bundle.js
</code-example>

Run the explorer to generate a graphical representation of one of the bundles.
The following example displays the graph for the _main_ bundle.

<code-example language="none" class="code-shell">
  node_modules/.bin/source-map-explorer dist/main.*.bundle.js
</code-example>

The `source-map-explorer` analyzes the source map generated with the bundle and draws a map of all dependencies,
showing exactly which classes are included in the bundle.

Here's the output for the _main_ bundle of the QuickStart.

<figure>
  <img src="generated/images/guide/cli-quickstart/quickstart-sourcemap-explorer.png" alt="quickstart sourcemap explorer">
</figure>

{@a base-tag}

## The `base` tag

The HTML [_&lt;base href="..."/&gt;_](/guide/router)
specifies a base path for resolving relative URLs to assets such as images, scripts, and style sheets.
For example, given the `<base href="/my/app/">`, the browser resolves a URL such as `some/place/foo.jpg`
into a server request for `my/app/some/place/foo.jpg`.
During navigation, the Angular router uses the _base href_ as the base path to component, template, and module files.

<div class="alert is-helpful">

See also the [*APP_BASE_HREF*](api/common/APP_BASE_HREF "API: APP_BASE_HREF") alternative.

</div>

In development, you typically start the server in the folder that holds `index.html`.
That's the root folder and you'd add `<base href="/">` near the top of `index.html` because `/` is the root of the app.

But on the shared or production server, you might serve the app from a subfolder.
For example, when the URL to load the app is something like `http://www.mysite.com/my/app/`,
the subfolder is `my/app/` and you should add `<base href="/my/app/">` to the server version of the `index.html`.

When the `base` tag is mis-configured, the app fails to load and the browser console displays `404 - Not Found` errors
for the missing files. Look at where it _tried_ to find those files and adjust the base tag appropriately.

## Differential Loading

When building web applications, making sure your application is compatible with the majority of browsers is a goal. Even as JavaScript continues to evolve, with new features being introduced, not all browsers are updated with support for these new features at the same pace. This is where compilation and [polyfills](guide/browser-support#polyfills) come in. The code you write in development using TypeScript is compiled and bundled into a format that is compatible with most browsers, commonly known as ES5. Polyfills are used bridge the gap, providing functionality that simply doesn't exist in some legacy browsers. 

There is a cost to ensure this browser compatibility, and it comes in the form of larger bundle size. All modern browsers support ES2015 and beyond, but in most cases, you still have to account for users accessing your application from a browser that doesn't. To maximize compatibility, you ship a single bundle that includes all your compiled code, plus any polyfills that may be needed. Users with modern browsers shouldn't pay the price of increased bundle size when used in a modern browser that supports many of the latest features in JavaScript. This is where differential loading comes into play.

Differential loading is a strategy where the CLI builds two separate bundles as part of your deployed application. The modern bundle contains modern syntax, takes advantage of built-in support in modern browsers, ships less polyfills, and results in a smaller bundle size. The second bundle, includes the additional compiled code, all necessary polyfills, and results in a larger bundle size. This strategy allows you to continue to build your web application to support multiple browsers, but only load the necessary code that the browser needs.

### Differential builds

The Angular CLI handles differential loading for you as part of the _build_ process for deployment. The Angular CLI will produce the necessary bundles used for differential loading, based on your browser support requirements and compilation target. 

The Angular CLI uses two configurations for differential loading:

- Browserslist - The `browserslist` configuration file is included in your application [project structure](guide/file-structure#application-configuration-files) and provides the minimum browsers your application supports. See the [Browserslist spec](https://github.com/browserslist/browserslist) for complete configuration options.
- tsconfig.json - The `target` in the TypeScript `compilerOptions` determines the ECMAScript target version that the code is compiled to. Modern browsers support ES2015 natively, while ES5 is more commonly used to support legacy browsers.

<div class="alert is-helpful">

**Note:** Differential loading is currently only supported when using `es2015` as a compilation `target`. When used with targets higher than `es2015`, a warning is emitted during build time.

</div>

The CLI queries the Browserslist configuration, and checks the `target` to determine if support for legacy browsers is required. The combination of these two configurations determines whether multiple bundles are produced when you create a _build_. When you create a development build using [`ng build`](cli/build) and differential loading is enabled, the output produced is simpler and easier to debug, allowing you to rely less on sourcemaps of compiled code. When you create a production build using [`ng build --prod`](cli/build), the CLI uses the defined configurations above to determine the bundles to build for deployment of your application. 

The `index.html` file is also modified during the build process to include script tags that enable differential loading. See the sample output below from the `index.html` file produced during a build using `ng build`.

```html
<!-- ... -->
<body>
  <app-root></app-root>
  <script src="runtime-es2015.js" type="module"></script>
  <script src="runtime-es5.js" nomodule></script>
  <script src="polyfills-es2015.js" type="module"></script>
  <script src="polyfills-es5.js" nomodule></script>
  <script src="styles-es2015.js" type="module"></script>
  <script src="styles-es5.js" nomodule></script>
  <script src="vendor-es2015.js" type="module"></script>
  <script src="vendor-es5.js" nomodule></script>
  <script src="main-es2015.js" type="module"></script>
  <script src="main-es5.js" nomodule></script>
</body>
<!-- ... -->
```

Each script tag has a `type="module"` or `nomodule` attribute. Browsers with native support for ES modules only load the scripts with the `module` type attribute and ignore scripts with the `nomodule` attribute. Legacy browsers only load the scripts with the `nomodule` attribute, and ignore the script tags with the `module` type that load ES modules. 

<div class="alert is-helpful">

**Note:** Some legacy browsers still download both bundles, but only execute the appropriate scripts based on the attributes mentioned above. You can read more on the issue [here](https://github.com/philipwalton/webpack-esnext-boilerplate/issues/1).

</div>

See the [configuration table](#configuration-table) below for the configurations for enabling differential loading.

### Configuring differential loading

Differential loading for creating builds is already supported with version 8 and later of the Angular CLI. For each application project in your workspace, you can configure how builds are produced based on the mentioned `browserslist` and `tsconfig.json` files in your application project.

Look at the default configuration for a newly created Angular application:

The `browserslist` looks like this:

```
> 0.5%
last 2 versions
Firefox ESR
not dead
not IE 9-11 # For IE 9-11 support, remove 'not'.
```

The `tsconfig.json` looks like this:


```
{
  "compileOnSave": false,
  "compilerOptions": {
    "baseUrl": "./",
    "outDir": "./dist/out-tsc",
    "sourceMap": true,
    "declaration": false,
    "module": "esnext",
    "moduleResolution": "node",
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "importHelpers": true,
    "target": "es2015",
    "typeRoots": [
      "node_modules/@types"
    ],
    "lib": [
      "es2018",
      "dom"
    ]
  }
}
```

By default, legacy browsers such as IE 9-11 are ignored, and the compilation target is ES2015. As a result, this produces two builds, and differential loading is enabled. If you ignore browsers without ES2015 support, a single build is produced. To see the build result for differential loading based on different configurations, refer to the table below. 

<div class="alert is-important">

**Note:** To see which browsers are supported with the above configuration, see which settings meet to your browser support requirements, see the [Browserslist compatibility page](https://browserl.ist/?q=%3E+0.5%25%2C+last+2+versions%2C+Firefox+ESR%2C+Chrome+41%2C+not+dead%2C+not+IE+9-11).

</div>

{@a configuration-table }

| ES5 Browserslist Result | ES Target | Build Result |
| -------- | -------- | -------- |
| disabled | es5     | Single build |
| enabled  | es5     | Single build w/Conditional Polyfills |
| disabled | es2015  | Single build |
| enabled  | es2015  | Differential Loading (Two builds w/Conditional Polyfills |

When the ES5 Browserslist result is `disabled`, then ES5 browser support is not required. Otherwise, ES5 browser support is required.

### Opting out of differential loading

Differential loading can be explicitly disabled if it causes unexpected issues or you need to target ES5 specifically for legacy browser support. 

To explicitly disable differential loading:

- Enable the `dead` or `IE` browsers in the `browserslist` config file by removing the `not` keyword in front of them.
- Set the `target` in the `compilerOptions` to `es5`.