# 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`
`--extract-licenses` Extract all licenses in a separate file, in the case of production builds only.
`--i18n-file` Localization file to use for i18n.
`--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.
### 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.
## Options
aot
--aot default value: false
Build using Ahead of Time compilation.
app
--app (aliases: -a)
Specifies app name or index to use.
base-href
--base-href (aliases: -bh)
Base url for the application being built.
deploy-url
--deploy-url (aliases: -d)
URL where files will be deployed.
environment
--environment (aliases: -e)
Defines the build environment.
extract-css
--extract-css (aliases: -ec)
Extract css from global styles onto css files instead of js ones.
i18n-file
--i18n-file
Localization file to use for i18n.
i18n-format
--i18n-format
Format of the localization file specified with --i18n-file.
locale
--locale
Locale to use for i18n.
output-hashing
--output-hashing (aliases: -oh)
Define the output filename cache-busting hashing mode.
Values: none, all, media, bundles
output-path
--output-path (aliases: -op)
Path where output will be placed.
delete-output-path
--delete-output-path (aliases: -dop) default value: true
Delete the output-path directory.
poll
--poll
Enable and define the file watching poll time period (milliseconds).
progress
--progress (aliases: -pr) default value: true
Log progress to the console while building.
sourcemap
--sourcemap (aliases: -sm, sourcemaps)
Output sourcemaps.
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.
target
--target (aliases: -t, -dev, -prod) default value: development
Defines the build target.
vendor-chunk
--vendor-chunk (aliases: -vc) default value: true
Use a separate bundle containing only vendor libraries.
verbose
--verbose (aliases: -v) default value: false
Adds more details to output logging.
watch
--watch (aliases: -w)
Run build when files change.