# Content projection with ng-content

Tip: This guide assumes you've already read the [Essentials Guide](essentials). Read that first if you're new to Angular.

You often need to create components that act as containers for different types of content. For
example, you may want to create a custom card component:

```angular-ts
@Component({
  selector: 'custom-card',
  template: '<div class="card-shadow"> <!-- card content goes here --> </div>',
})
export class CustomCard {/* ... */}
```

**You can use the `<ng-content>` element as a placeholder to mark where content should go**:

```angular-ts
@Component({
  selector: 'custom-card',
  template: '<div class="card-shadow"> <ng-content></ng-content> </div>',
})
export class CustomCard {/* ... */}
```

Tip: `<ng-content>` works similarly
to [the native `<slot>` element](https://developer.mozilla.org/docs/Web/HTML/Element/slot),
but with some Angular-specific functionality.

When you use a component with `<ng-content>`, any children of the component host element are
rendered, or **projected**, at the location of that `<ng-content>`:

```angular-ts
// Component source
@Component({
  selector: 'custom-card',
  template: `
    <div class="card-shadow">
      <ng-content />
    </div>
  `,
})
export class CustomCard {/* ... */}
```

```angular-html
<!-- Using the component -->
<custom-card>
  <p>This is the projected content</p>
</custom-card>
```

```angular-html
<!-- The rendered DOM -->
<custom-card>
  <div class="card-shadow">
    <p>This is the projected content</p>
  </div>
</custom-card>
```

Angular refers to any children of a component passed this way as that component's **content**. This
is distinct from the component's **view**, which refers to the elements defined in the component's
template.

**The `<ng-content>` element is neither a component nor DOM element**. Instead, it is a special
placeholder that tells Angular where to render content. Angular's compiler processes
all `<ng-content>` elements at build-time. You cannot insert, remove, or modify `<ng-content>` at
run time. You cannot add directives, styles, or arbitrary attributes to `<ng-content>`.

You should not conditionally include `<ng-content>` with `@if`, `@for`, or `@switch`. Angular always
instantiates and creates DOM nodes for content rendered to a `<ng-content>` placeholder, even if
that `<ng-content>` placeholder is hidden. For conditional rendering of component content,
see [Template fragments](api/core/ng-template).

## Multiple content placeholders

Angular supports projecting multiple different elements into different `<ng-content>` placeholders
based on CSS selector. Expanding the card example from above, you could create two placeholders for
a card title and a card body by using the `select` attribute:

```angular-html
<!-- Component template -->
<div class="card-shadow">
  <ng-content select="card-title"></ng-content>
  <div class="card-divider"></div>
  <ng-content select="card-body"></ng-content>
</div>
```

```angular-html
<!-- Using the component -->
<custom-card>
  <card-title>Hello</card-title>
  <card-body>Welcome to the example</card-body>
</custom-card>
```

```angular-html
<!-- Rendered DOM -->
<custom-card>
  <div class="card-shadow">
    <card-title>Hello</card-title>
    <div class="card-divider"></div>
    <card-body>Welcome to the example</card-body>
  </div>
</custom-card>
```

The `<ng-content>` placeholder supports the same CSS selectors
as [component selectors](guide/components/selectors).

If you include one or more `<ng-content>` placeholders with a `select` attribute and
one `<ng-content>` placeholder without a `select` attribute, the latter captures all elements that
did not match a `select` attribute:

```angular-html
<!-- Component template -->
<div class="card-shadow">
  <ng-content select="card-title"></ng-content>
  <div class="card-divider"></div>
  <!-- capture anything except "card-title" -->
  <ng-content></ng-content>
</div>
```

```angular-html
<!-- Using the component -->
<custom-card>
  <card-title>Hello</card-title>
  <img src="..." />
  <p>Welcome to the example</p>
</custom-card>
```

```angular-html
<!-- Rendered DOM -->
<custom-card>
  <div class="card-shadow">
    <card-title>Hello</card-title>
    <div class="card-divider"></div>
    <img src="..." />
    <p>Welcome to the example></p>
  </div>
</custom-card>
```

If a component does not include an `<ng-content>` placeholder without a `select` attribute, any
elements that don't match one of the component's placeholders do not render into the DOM.

## Fallback content

Angular can show *fallback content* for a component's `<ng-content>` placeholder if that component doesn't have any matching child content. You can specify fallback content by adding child content to the `<ng-content>` element itself.

```angular-html
<!-- Component template -->
<div class="card-shadow">
  <ng-content select="card-title">Default Title</ng-content>
  <div class="card-divider"></div>
  <ng-content select="card-body">Default Body</ng-content>
</div>
```

```angular-html
<!-- Using the component -->
<custom-card>
  <card-title>Hello</card-title>
  <!-- No card-body provided -->
</custom-card>
```

```angular-html
<!-- Rendered DOM -->
<custom-card>
  <div class="card-shadow">
    Hello
    <div class="card-divider"></div>
    Default Body
  </div>
</custom-card>
```

## Aliasing content for projection

Angular supports a special attribute, `ngProjectAs`, that allows you to specify a CSS selector on
any element. Whenever an element with `ngProjectAs` is checked against an `<ng-content>`
placeholder, Angular compares against the `ngProjectAs` value instead of the element's identity:

```angular-html
<!-- Component template -->
<div class="card-shadow">
  <ng-content select="card-title"></ng-content>
  <div class="card-divider"></div>
  <ng-content></ng-content>
</div>
```

```angular-html
<!-- Using the component -->
<custom-card>
  <h3 ngProjectAs="card-title">Hello</h3>

  <p>Welcome to the example</p>
</custom-card>
```

```angular-html
<!-- Rendered DOM -->
<custom-card>
  <div class="card-shadow">
    <h3>Hello</h3>
    <div class="card-divider"></div>
    <p>Welcome to the example></p>
  </div>
</custom-card>
```

`ngProjectAs` supports only static values and cannot be bound to dynamic expressions.
