# ng build
## Overview
`ng build` compiles the application into an output directory.
### Creating a build
```bash
ng build
```
The build artifacts will be stored in the `dist/` directory.
All commands that build or serve your project, `ng build/serve/e2e`, will delete the output
directory (`dist/` by default).
This can be disabled via the `--no-delete-output-path` (or `--delete-output-path=false`) flag.
### Build Targets and Environment Files
`ng build` can specify both a build target (`--target=production` or `--target=development`) and an
environment file to be used with that build (`--environment=dev` or `--environment=prod`).
By default, the development build target and environment are used.
The mapping used to determine which environment file is used can be found in `.angular-cli.json`:
```json
"environmentSource": "environments/environment.ts",
"environments": {
"dev": "environments/environment.ts",
"prod": "environments/environment.prod.ts"
}
```
These options also apply to the serve command. If you do not pass a value for `environment`,
it will default to `dev` for `development` and `prod` for `production`.
```bash
# these are equivalent
ng build --target=production --environment=prod
ng build --prod --env=prod
ng build --prod
# and so are these
ng build --target=development --environment=dev
ng build --dev --e=dev
ng build --dev
ng build
```
You can also add your own env files other than `dev` and `prod` by doing the following:
- create a `src/environments/environment.NAME.ts`
- add `{ "NAME": 'src/environments/environment.NAME.ts' }` to the `apps[0].environments` object in `.angular-cli.json`
- use them via the `--env=NAME` flag on the build/serve commands.
### Base tag handling in index.html
When building you can modify base tag (``) in your index.html with `--base-href your-url` option.
```bash
# Sets base tag href to /myUrl/ in your index.html
ng build --base-href /myUrl/
ng build --bh /myUrl/
```
### Bundling & Tree-Shaking
All builds make use of bundling and limited tree-shaking, while `--prod` builds also run limited
dead code elimination via UglifyJS.
### `--dev` vs `--prod` builds
Both `--dev`/`--target=development` and `--prod`/`--target=production` are 'meta' flags, that set other flags.
If you do not specify either you will get the `--dev` defaults.
Flag | `--dev` | `--prod`
--- | --- | ---
`--aot` | `false` | `true`
`--environment` | `dev` | `prod`
`--output-hashing` | `media` | `all`
`--sourcemaps` | `true` | `false`
`--extract-css` | `false` | `true`
`--named-chunks` | `true` | `false`
`--build-optimizer` | `false` | `true` with AOT and Angular 5
`--prod` also sets the following non-flaggable settings:
- Adds service worker if configured in `.angular-cli.json`.
- Replaces `process.env.NODE_ENV` in modules with the `production` value (this is needed for some libraries, like react).
- Runs UglifyJS on the code.
### `--build-optimizer` and `--vendor-chunk`
When using Build Optimizer the vendor chunk will be disabled by default.
You can override this with `--vendor-chunk=true`.
Total bundle sizes with Build Optimizer are smaller if there is no separate vendor chunk because
having vendor code in the same chunk as app code makes it possible for Uglify to remove more unused
code.
### CSS resources
Resources in CSS, such as images and fonts, will be copied over automatically as part of a build.
If a resource is less than 10kb it will also be inlined.
You'll see these resources be outputted and fingerprinted at the root of `dist/`.
### Service Worker
There is experimental service worker support for production builds available in the CLI.
To enable it, run the following commands:
```
npm install @angular/service-worker --save
ng set apps.0.serviceWorker=true
```
On `--prod` builds a service worker manifest will be created and loaded automatically.
Remember to disable the service worker while developing to avoid stale code.
Note: service worker support is experimental and subject to change.
### ES2015 support
To build in ES2015 mode, edit `./tsconfig.json` to use `"target": "es2015"` (instead of `es5`).
This will cause application TypeScript and Uglify be output as ES2015, and third party libraries
to be loaded through the `es2015` entry in `package.json` if available.
Be aware that JIT does not support ES2015 and so you should build/serve your app with `--aot`.
See https://github.com/angular/angular-cli/issues/7797 for details.
## Options
prod
--prod
Flag to set configuration to "prod".
configuration
--configuration (alias: -c)
Specify the configuration to use.
main
--main
The name of the main entry-point file.
polyfills
--polyfills
The name of the polyfills file.
ts-config
--ts-config
The name of the TypeScript configuration file.
optimization
--optimization
Defines the optimization level of the build.
output-path
--output-path
Path where output will be placed.
aot
--aot
Build using Ahead of Time compilation.
source-map
--source-map
Output sourcemaps.
eval-source-map
--eval-source-map
Output in-file eval sourcemaps.
vendor-chunk
--vendor-chunk
Use a separate bundle containing only vendor libraries.
common-chunk
--common-chunk
Use a separate bundle containing code used across multiple bundles.
base-href
--base-href
Base url for the application being built.
deploy-url
--deploy-url
URL where files will be deployed.
verbose
--verbose
Adds more details to output logging.
progress
--progress
Log progress to the console while building.
i18n-file
--i18n-file
Localization file to use for i18n.
i18n-format
--i18n-format
Format of the localization file specified with --i18n-file.
i18n-locale
--i18n-locale
Locale to use for i18n.
i18n-missing-translation
--i18n-missing-translation
How to handle missing translations for i18n.
extract-css
--extract-css
Extract css from global styles onto css files instead of js ones.
watch
--watch
Run build when files change.
output-hashing
--output-hashing
Define the output filename cache-busting hashing mode.
poll
--poll
Enable and define the file watching poll time period in milliseconds.
delete-output-path
--delete-output-path
Delete the output path before building.
preserve-symlinks
--preserve-symlinks
Do not use the real path when resolving modules.
extract-licenses
--extract-licenses
Extract all licenses in a separate file, in the case of production builds only.
show-circular-dependencies
--show-circular-dependencies
Show circular dependency warnings on builds.
build-optimizer
--build-optimizer
Enables @angular-devkit/build-optimizer optimizations when using the 'aot' option.
named-chunks
--named-chunks
Use file name for lazy loaded chunks.
subresource-integrity
--subresource-integrity
Enables the use of subresource integrity validation.
service-worker
--service-worker
Generates a service worker config for production builds.
ngsw-config-path
--ngsw-config-path
Path to ngsw-config.json.
skip-app-shell
--skip-app-shell
Flag to prevent building an app shell.
index
--index
The name of the index HTML file.
stats-json
--stats-json
Generates a 'stats.json' file which can be analyzed using tools such as: #webpack-bundle-analyzer' or https: //webpack.github.io/analyse.
fork-type-checker
--fork-type-checker
Run the TypeScript type checker in a forked process.