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6 years ago
# reveal.js [![Build Status](https://travis-ci.org/hakimel/reveal.js.svg?branch=master)](https://travis-ci.org/hakimel/reveal.js) <a href="https://slides.com?ref=github"><img src="https://s3.amazonaws.com/static.slid.es/images/slides-github-banner-320x40.png?1" alt="Slides" width="160" height="20"></a>
A framework for easily creating beautiful presentations using HTML. [Check out the live demo](http://revealjs.com/).
11 years ago
reveal.js comes with a broad range of features including [nested slides](https://github.com/hakimel/reveal.js#markup), [Markdown contents](https://github.com/hakimel/reveal.js#markdown), [PDF export](https://github.com/hakimel/reveal.js#pdf-export), [speaker notes](https://github.com/hakimel/reveal.js#speaker-notes) and a [JavaScript API](https://github.com/hakimel/reveal.js#api). There's also a fully featured visual editor and platform for sharing reveal.js presentations at [slides.com](https://slides.com?ref=github).
11 years ago
## Table of contents
- [Online Editor](#online-editor)
- [Installation](#installation)
- [Basic setup](#basic-setup)
- [Full setup](#full-setup)
- [Folder Structure](#folder-structure)
- [Instructions](#instructions)
- [Markup](#markup)
- [Markdown](#markdown)
- [Element Attributes](#element-attributes)
- [Slide Attributes](#slide-attributes)
- [Configuration](#configuration)
- [Presentation Size](#presentation-size)
- [Dependencies](#dependencies)
- [Ready Event](#ready-event)
- [Auto-sliding](#auto-sliding)
- [Keyboard Bindings](#keyboard-bindings)
- [Vertical Slide Navigation](#vertical-slide-navigation)
- [Touch Navigation](#touch-navigation)
- [Lazy Loading](#lazy-loading)
- [API](#api)
- [Slide Changed Event](#slide-changed-event)
- [Presentation State](#presentation-state)
- [Slide States](#slide-states)
- [Slide Backgrounds](#slide-backgrounds)
- [Parallax Background](#parallax-background)
- [Slide Transitions](#slide-transitions)
- [Internal links](#internal-links)
- [Fragments](#fragments)
- [Fragment events](#fragment-events)
- [Code syntax highlighting](#code-syntax-highlighting)
- [Slide number](#slide-number)
- [Overview mode](#overview-mode)
- [Fullscreen mode](#fullscreen-mode)
- [Embedded media](#embedded-media)
- [Stretching elements](#stretching-elements)
- [Resize Event](#resize-event)
- [postMessage API](#postmessage-api)
- [PDF Export](#pdf-export)
- [Theming](#theming)
- [Speaker Notes](#speaker-notes)
- [Share and Print Speaker Notes](#share-and-print-speaker-notes)
- [Server Side Speaker Notes](#server-side-speaker-notes)
- [Multiplexing](#multiplexing)
- [Master presentation](#master-presentation)
- [Client presentation](#client-presentation)
- [Socket.io server](#socketio-server)
- [MathJax](#mathjax)
- [License](#license)
11 years ago
#### More reading
- [Changelog](https://github.com/hakimel/reveal.js/releases): Up-to-date version history.
10 years ago
- [Examples](https://github.com/hakimel/reveal.js/wiki/Example-Presentations): Presentations created with reveal.js, add your own!
- [Browser Support](https://github.com/hakimel/reveal.js/wiki/Browser-Support): Explanation of browser support and fallbacks.
7 years ago
- [Plugins](https://github.com/hakimel/reveal.js/wiki/Plugins,-Tools-and-Hardware): A list of plugins that can be used to extend reveal.js.
## Online Editor
Presentations are written using HTML or Markdown but there's also an online editor for those of you who prefer a graphical interface. Give it a try at [https://slides.com](https://slides.com?ref=github).
## Installation
The **basic setup** is for authoring presentations only. The **full setup** gives you access to all reveal.js features and plugins such as speaker notes as well as the development tasks needed to make changes to the source.
### Basic setup
The core of reveal.js is very easy to install. You'll simply need to download a copy of this repository and open the index.html file directly in your browser.
1. Download the latest version of reveal.js from <https://github.com/hakimel/reveal.js/releases>
2. Unzip and replace the example contents in index.html with your own
3. Open index.html in a browser to view it
### Full setup
Some reveal.js features, like external Markdown and speaker notes, require that presentations run from a local web server. The following instructions will set up such a server as well as all of the development tasks needed to make edits to the reveal.js source code.
1. Install [Node.js](http://nodejs.org/) (4.0.0 or later)
1. Clone the reveal.js repository
```sh
$ git clone https://github.com/hakimel/reveal.js.git
```
1. Navigate to the reveal.js folder
```sh
$ cd reveal.js
```
1. Install dependencies
```sh
$ npm install
```
1. Serve the presentation and monitor source files for changes
```sh
$ npm start
```
1. Open <http://localhost:8000> to view your presentation
You can change the port by using `npm start -- --port=8001`.
### Folder Structure
- **css/** Core styles without which the project does not function
- **js/** Like above but for JavaScript
- **plugin/** Components that have been developed as extensions to reveal.js
- **lib/** All other third party assets (JavaScript, CSS, fonts)
## Instructions
### Markup
Here's a barebones example of a fully working reveal.js presentation:
```html
<html>
<head>
<link rel="stylesheet" href="css/reveal.css">
<link rel="stylesheet" href="css/theme/white.css">
</head>
<body>
<div class="reveal">
<div class="slides">
<section>Slide 1</section>
<section>Slide 2</section>
</div>
</div>
<script src="js/reveal.js"></script>
<script>
Reveal.initialize();
</script>
</body>
</html>
```
7 years ago
The presentation markup hierarchy needs to be `.reveal > .slides > section` where the `section` represents one slide and can be repeated indefinitely. If you place multiple `section` elements inside of another `section` they will be shown as vertical slides. The first of the vertical slides is the "root" of the others (at the top), and will be included in the horizontal sequence. For example:
```html
<div class="reveal">
<div class="slides">
<section>Single Horizontal Slide</section>
<section>
<section>Vertical Slide 1</section>
<section>Vertical Slide 2</section>
</section>
</div>
</div>
```
### Markdown
It's possible to write your slides using Markdown. To enable Markdown, add the `data-markdown` attribute to your `<section>` elements and wrap the contents in a `<textarea data-template>` like the example below. You'll also need to add the `plugin/markdown/marked.js` and `plugin/markdown/markdown.js` scripts (in that order) to your HTML file.
This is based on [data-markdown](https://gist.github.com/1343518) from [Paul Irish](https://github.com/paulirish) modified to use [marked](https://github.com/chjj/marked) to support [GitHub Flavored Markdown](https://help.github.com/articles/github-flavored-markdown). Sensitive to indentation (avoid mixing tabs and spaces) and line breaks (avoid consecutive breaks).
```html
<section data-markdown>
<textarea data-template>
## Page title
A paragraph with some text and a [link](http://hakim.se).
</textarea>
</section>
```
#### External Markdown
You can write your content as a separate file and have reveal.js load it at runtime. Note the separator arguments which determine how slides are delimited in the external file: the `data-separator` attribute defines a regular expression for horizontal slides (defaults to `^\r?\n---\r?\n$`, a newline-bounded horizontal rule) and `data-separator-vertical` defines vertical slides (disabled by default). The `data-separator-notes` attribute is a regular expression for specifying the beginning of the current slide's speaker notes (defaults to `notes?:`, so it will match both "note:" and "notes:"). The `data-charset` attribute is optional and specifies which charset to use when loading the external file.
When used locally, this feature requires that reveal.js [runs from a local web server](#full-setup). The following example customises all available options:
```html
<section data-markdown="example.md"
data-separator="^\n\n\n"
data-separator-vertical="^\n\n"
data-separator-notes="^Note:"
data-charset="iso-8859-15">
<!--
Note that Windows uses `\r\n` instead of `\n` as its linefeed character.
For a regex that supports all operating systems, use `\r?\n` instead of `\n`.
-->
</section>
```
#### Element Attributes
Special syntax (through HTML comments) is available for adding attributes to Markdown elements. This is useful for fragments, amongst other things.
```html
<section data-markdown>
<script type="text/template">
- Item 1 <!-- .element: class="fragment" data-fragment-index="2" -->
- Item 2 <!-- .element: class="fragment" data-fragment-index="1" -->
</script>
</section>
```
#### Slide Attributes
Special syntax (through HTML comments) is available for adding attributes to the slide `<section>` elements generated by your Markdown.
```html
<section data-markdown>
<script type="text/template">
<!-- .slide: data-background="#ff0000" -->
8 years ago
Markdown content
</script>
</section>
```
#### Configuring *marked*
We use [marked](https://github.com/chjj/marked) to parse Markdown. To customise marked's rendering, you can pass in options when [configuring Reveal](#configuration):
```javascript
Reveal.initialize({
// Options which are passed into marked
// See https://marked.js.org/#/USING_ADVANCED.md#options
markdown: {
smartypants: true
}
});
```
### Configuration
At the end of your page you need to initialize reveal by running the following code. Note that all configuration values are optional and will default to the values specified below.
```javascript
Reveal.initialize({
// Display presentation control arrows
controls: true,
// Help the user learn the controls by providing hints, for example by
// bouncing the down arrow when they first encounter a vertical slide
controlsTutorial: true,
// Determines where controls appear, "edges" or "bottom-right"
controlsLayout: 'bottom-right',
// Visibility rule for backwards navigation arrows; "faded", "hidden"
// or "visible"
controlsBackArrows: 'faded',
// Display a presentation progress bar
progress: true,
// Display the page number of the current slide
slideNumber: false,
// Add the current slide number to the URL hash so that reloading the
// page/copying the URL will return you to the same slide
hash: false,
// Push each slide change to the browser history. Implies `hash: true`
history: false,
// Enable keyboard shortcuts for navigation
keyboard: true,
// Enable the slide overview mode
overview: true,
// Vertical centering of slides
center: true,
// Enables touch navigation on devices with touch input
touch: true,
// Loop the presentation
loop: false,
// Change the presentation direction to be RTL
rtl: false,
// See https://github.com/hakimel/reveal.js/#navigation-mode
navigationMode: 'default',
// Randomizes the order of slides each time the presentation loads
shuffle: false,
// Turns fragments on and off globally
fragments: true,
// Flags whether to include the current fragment in the URL,
// so that reloading brings you to the same fragment position
fragmentInURL: false,
// Flags if the presentation is running in an embedded mode,
// i.e. contained within a limited portion of the screen
embedded: false,
// Flags if we should show a help overlay when the questionmark
// key is pressed
help: true,
// Flags if speaker notes should be visible to all viewers
showNotes: false,
5 years ago
// Global override for autoplaying embedded media (video/audio/iframe)
// - null: Media will only autoplay if data-autoplay is present
// - true: All media will autoplay, regardless of individual setting
// - false: No media will autoplay, regardless of individual setting
autoPlayMedia: null,
// Number of milliseconds between automatically proceeding to the
// next slide, disabled when set to 0, this value can be overwritten
// by using a data-autoslide attribute on your slides
autoSlide: 0,
// Stop auto-sliding after user input
autoSlideStoppable: true,
// Use this method for navigation when auto-sliding
autoSlideMethod: Reveal.navigateNext,
// Specify the average time in seconds that you think you will spend
// presenting each slide. This is used to show a pacing timer in the
// speaker view
defaultTiming: 120,
// Enable slide navigation via mouse wheel
mouseWheel: false,
// Hide cursor if inactive
hideInactiveCursor: true,
// Time before the cursor is hidden (in ms)
hideCursorTime: 5000,
// Hides the address bar on mobile devices
hideAddressBar: true,
// Opens links in an iframe preview overlay
// Add `data-preview-link` and `data-preview-link="false"` to customise each link
// individually
previewLinks: false,
// Transition style
transition: 'slide', // none/fade/slide/convex/concave/zoom
// Transition speed
transitionSpeed: 'default', // default/fast/slow
// Transition style for full page slide backgrounds
backgroundTransition: 'fade', // none/fade/slide/convex/concave/zoom
// Number of slides away from the current that are visible
viewDistance: 3,
// Parallax background image
parallaxBackgroundImage: '', // e.g. "'https://s3.amazonaws.com/hakim-static/reveal-js/reveal-parallax-1.jpg'"
// Parallax background size
parallaxBackgroundSize: '', // CSS syntax, e.g. "2100px 900px"
// Number of pixels to move the parallax background per slide
// - Calculated automatically unless specified
// - Set to 0 to disable movement along an axis
parallaxBackgroundHorizontal: null,
parallaxBackgroundVertical: null,
// The display mode that will be used to show slides
display: 'block'
});
```
The configuration can be updated after initialization using the `configure` method:
```javascript
// Turn autoSlide off
Reveal.configure({ autoSlide: 0 });
// Start auto-sliding every 5s
Reveal.configure({ autoSlide: 5000 });
```
### Presentation Size
All presentations have a normal size, that is, the resolution at which they are authored. The framework will automatically scale presentations uniformly based on this size to ensure that everything fits on any given display or viewport.
See below for a list of configuration options related to sizing, including default values:
```javascript
Reveal.initialize({
// ...
// The "normal" size of the presentation, aspect ratio will be preserved
// when the presentation is scaled to fit different resolutions. Can be
// specified using percentage units.
width: 960,
height: 700,
// Factor of the display size that should remain empty around the content
margin: 0.1,
// Bounds for smallest/largest possible scale to apply to content
minScale: 0.2,
maxScale: 1.5
});
```
If you wish to disable this behavior and do your own scaling (e.g. using media queries), try these settings:
```javascript
Reveal.initialize({
// ...
width: "100%",
height: "100%",
margin: 0,
minScale: 1,
maxScale: 1
});
```
### Dependencies
Reveal.js doesn't _rely_ on any third party scripts to work but a few optional libraries are included by default. These libraries are loaded as dependencies in the order they appear, for example:
```javascript
Reveal.initialize({
dependencies: [
10 years ago
// Interpret Markdown in <section> elements
{ src: 'plugin/markdown/marked.js', condition: function() { return !!document.querySelector( '[data-markdown]' ); } },
{ src: 'plugin/markdown/markdown.js', condition: function() { return !!document.querySelector( '[data-markdown]' ); } },
// Syntax highlight for <code> elements
{ src: 'plugin/highlight/highlight.js', async: true, callback: function() { hljs.initHighlightingOnLoad(); } },
// Zoom in and out with Alt+click
{ src: 'plugin/zoom-js/zoom.js', async: true },
// Speaker notes
{ src: 'plugin/notes/notes.js', async: true },
// MathJax
{ src: 'plugin/math/math.js', async: true }
]
});
```
You can add your own extensions using the same syntax. The following properties are available for each dependency object:
- **src**: Path to the script to load
- **async**: [optional] Flags if the script should load after reveal.js has started, defaults to false
- **callback**: [optional] Function to execute when the script has loaded
- **condition**: [optional] Function which must return true for the script to be loaded
### Ready Event
A `ready` event is fired when reveal.js has loaded all non-async dependencies and is ready to start navigating. To check if reveal.js is already 'ready' you can call `Reveal.isReady()`.
```javascript
Reveal.addEventListener( 'ready', function( event ) {
// event.currentSlide, event.indexh, event.indexv
} );
```
Note that we also add a `.ready` class to the `.reveal` element so that you can hook into this with CSS.
### Auto-sliding
Presentations can be configured to progress through slides automatically, without any user input. To enable this you will need to tell the framework how many milliseconds it should wait between slides:
```javascript
// Slide every five seconds
Reveal.configure({
autoSlide: 5000
});
```
When this is turned on a control element will appear that enables users to pause and resume auto-sliding. Alternatively, sliding can be paused or resumed by pressing »A« on the keyboard. Sliding is paused automatically as soon as the user starts navigating. You can disable these controls by specifying `autoSlideStoppable: false` in your reveal.js config.
You can also override the slide duration for individual slides and fragments by using the `data-autoslide` attribute:
```html
9 years ago
<section data-autoslide="2000">
<p>After 2 seconds the first fragment will be shown.</p>
<p class="fragment" data-autoslide="10000">After 10 seconds the next fragment will be shown.</p>
<p class="fragment">Now, the fragment is displayed for 2 seconds before the next slide is shown.</p>
</section>
```
To override the method used for navigation when auto-sliding, you can specify the `autoSlideMethod` setting. To only navigate along the top layer and ignore vertical slides, set this to `Reveal.navigateRight`.
Whenever the auto-slide mode is resumed or paused the `autoslideresumed` and `autoslidepaused` events are fired.
### Keyboard Bindings
If you're unhappy with any of the default keyboard bindings you can override them using the `keyboard` config option:
```javascript
Reveal.configure({
keyboard: {
13: 'next', // go to the next slide when the ENTER key is pressed
27: function() {}, // do something custom when ESC is pressed
32: null // don't do anything when SPACE is pressed (i.e. disable a reveal.js default binding)
}
});
```
### Vertical Slide Navigation
Slides can be nested within other slides to create vertical stacks (see [Markup](#markup)). When presenting, you use the left/right arrows to step through the main (horizontal) slides. When you arrive at a vertical stack you can optionally press the up/down arrows to view the vertical slides or skip past them by pressing the right arrow. Here's an example showing a bird's-eye view of what this looks like in action:
<img src="https://static.slid.es/support/reveal.js-vertical-slides.gif" width="450">
#### Navigation Mode
You can finetune the reveal.js navigation behavior by using the `navigationMode` config option. Note that these options are only useful for presnetations that use a mix of horizontal and vertical slides. The following navigation modes are available:
| Value | Description |
| :--------------------------- | :---------- |
| default | Left/right arrow keys step between horizontal slides. Up/down arrow keys step between vertical slides. Space key steps through all slides (both horizontal and vertical). |
| linear | Removes the up/down arrows. Left/right arrows step through all slides (both horizontal and vertical). |
| grid | When this is enabled, stepping left/right from a vertical stack to an adjacent vertical stack will land you at the same vertical index.<br><br>Consider a deck with six slides ordered in two vertical stacks:<br>`1.1`&nbsp;&nbsp;&nbsp;&nbsp;`2.1`<br>`1.2`&nbsp;&nbsp;&nbsp;&nbsp;`2.2`<br>`1.3`&nbsp;&nbsp;&nbsp;&nbsp;`2.3`<br><br>If you're on slide 1.3 and navigate right, you will normally move from 1.3 -> 2.1. With navigationMode set to "grid" the same navigation takes you from 1.3 -> 2.3. |
### Touch Navigation
You can swipe to navigate through a presentation on any touch-enabled device. Horizontal swipes change between horizontal slides, vertical swipes change between vertical slides. If you wish to disable this you can set the `touch` config option to false when initializing reveal.js.
If there's some part of your content that needs to remain accessible to touch events you'll need to highlight this by adding a `data-prevent-swipe` attribute to the element. One common example where this is useful is elements that need to be scrolled.
### Lazy Loading
When working on presentation with a lot of media or iframe content it's important to load lazily. Lazy loading means that reveal.js will only load content for the few slides nearest to the current slide. The number of slides that are preloaded is determined by the `viewDistance` configuration option.
To enable lazy loading all you need to do is change your `src` attributes to `data-src` as shown below. This is supported for image, video, audio and iframe elements.
```html
<section>
<img data-src="image.png">
<iframe data-src="http://hakim.se"></iframe>
<video>
<source data-src="video.webm" type="video/webm" />
<source data-src="video.mp4" type="video/mp4" />
</video>
</section>
```
#### Lazy Loading Iframes
Note that lazy loaded iframes ignore the `viewDistance` configuration and will only load when their containing slide becomes visible. Iframes are also unloaded as soon as the slide is hidden.
When we lazy load a video or audio element, reveal.js won't start playing that content until the slide becomes visible. However there is no way to control this for an iframe since that could contain any kind of content. That means if we loaded an iframe before the slide is visible on screen it could begin playing media and sound in the background.
### API
The `Reveal` object exposes a JavaScript API for controlling navigation and reading state:
```javascript
// Navigation
10 years ago
Reveal.slide( indexh, indexv, indexf );
Reveal.left();
Reveal.right();
Reveal.up();
Reveal.down();
Reveal.prev();
Reveal.next();
Reveal.prevFragment();
Reveal.nextFragment();
// Randomize the order of slides
Reveal.shuffle();
// Toggle presentation states, optionally pass true/false to force on/off
Reveal.toggleOverview();
9 years ago
Reveal.togglePause();
9 years ago
Reveal.toggleAutoSlide();
// Shows a help overlay with keyboard shortcuts, optionally pass true/false
// to force on/off
Reveal.toggleHelp();
// Change a config value at runtime
Reveal.configure({ controls: true });
// Returns the present configuration options
Reveal.getConfig();
// Fetch the current scale of the presentation
Reveal.getScale();
// Retrieves the previous and current slide elements
Reveal.getPreviousSlide();
Reveal.getCurrentSlide();
Reveal.getIndices(); // { h: 0, v: 0, f: 0 }
Reveal.getSlidePastCount();
Reveal.getProgress(); // (0 == first slide, 1 == last slide)
Reveal.getSlides(); // Array of all slides
Reveal.getTotalSlides(); // Total number of slides
9 years ago
// Returns the speaker notes for the current slide
Reveal.getSlideNotes();
9 years ago
// State checks
Reveal.isFirstSlide();
Reveal.isLastSlide();
Reveal.isOverview();
Reveal.isPaused();
Reveal.isAutoSliding();
// Returns the top-level DOM element
getRevealElement(); // <div class="reveal">...</div>
```
### Custom Key Bindings
Custom key bindings can be added and removed using the following Javascript API. Custom key bindings will override the default keyboard bindings, but will in turn be overridden by the user defined bindings in the ``keyboard`` config option.
```javascript
Reveal.addKeyBinding( binding, callback );
Reveal.removeKeyBinding( keyCode );
```
For example
```javascript
// The binding parameter provides the following properties
// keyCode: the keycode for binding to the callback
// key: the key label to show in the help overlay
// description: the description of the action to show in the help overlay
Reveal.addKeyBinding( { keyCode: 84, key: 'T', description: 'Start timer' }, function() {
// start timer
} )
// The binding parameter can also be a direct keycode without providing the help description
Reveal.addKeyBinding( 82, function() {
// reset timer
} )
```
This allows plugins to add key bindings directly to Reveal so they can
* make use of Reveal's pre-processing logic for key handling (for example, ignoring key presses when paused); and
* be included in the help overlay (optional)
### Slide Changed Event
A `slidechanged` event is fired each time the slide is changed (regardless of state). The event object holds the index values of the current slide as well as a reference to the previous and current slide HTML nodes.
Some libraries, like MathJax (see [#226](https://github.com/hakimel/reveal.js/issues/226#issuecomment-10261609)), get confused by the transforms and display states of slides. Often times, this can be fixed by calling their update or render function from this callback.
```javascript
Reveal.addEventListener( 'slidechanged', function( event ) {
// event.previousSlide, event.currentSlide, event.indexh, event.indexv
} );
```
### Presentation State
The presentation's current state can be fetched by using the `getState` method. A state object contains all of the information required to put the presentation back as it was when `getState` was first called. Sort of like a snapshot. It's a simple object that can easily be stringified and persisted or sent over the wire.
```javascript
Reveal.slide( 1 );
// we're on slide 1
var state = Reveal.getState();
Reveal.slide( 3 );
// we're on slide 3
Reveal.setState( state );
// we're back on slide 1
```
### Slide States
If you set `data-state="somestate"` on a slide `<section>`, "somestate" will be applied as a class on the document element when that slide is opened. This allows you to apply broad style changes to the page based on the active slide.
Furthermore you can also listen to these changes in state via JavaScript:
```javascript
Reveal.addEventListener( 'somestate', function() {
// TODO: Sprinkle magic
}, false );
```
### Slide Backgrounds
Slides are contained within a limited portion of the screen by default to allow them to fit any display and scale uniformly. You can apply full page backgrounds outside of the slide area by adding a `data-background` attribute to your `<section>` elements. Four different types of backgrounds are supported: color, image, video and iframe.
#### Color Backgrounds
All CSS color formats are supported, including hex values, keywords, `rgba()` or `hsl()`.
```html
<section data-background-color="#ff0000">
<h2>Color</h2>
</section>
```
#### Image Backgrounds
By default, background images are resized to cover the full page. Available options:
| Attribute | Default | Description |
| :------------------------------- | :--------- | :---------- |
| data-background-image | | URL of the image to show. GIFs restart when the slide opens. |
| data-background-size | cover | See [background-size](https://developer.mozilla.org/docs/Web/CSS/background-size) on MDN. |
| data-background-position | center | See [background-position](https://developer.mozilla.org/docs/Web/CSS/background-position) on MDN. |
| data-background-repeat | no-repeat | See [background-repeat](https://developer.mozilla.org/docs/Web/CSS/background-repeat) on MDN. |
| data-background-opacity | 1 | Opacity of the background image on a 0-1 scale. 0 is transparent and 1 is fully opaque. |
```html
<section data-background-image="http://example.com/image.png">
<h2>Image</h2>
</section>
<section data-background-image="http://example.com/image.png" data-background-size="100px" data-background-repeat="repeat">
<h2>This background image will be sized to 100px and repeated</h2>
</section>
```
#### Video Backgrounds
Automatically plays a full size video behind the slide.
| Attribute | Default | Description |
| :--------------------------- | :------ | :---------- |
| data-background-video | | A single video source, or a comma separated list of video sources. |
| data-background-video-loop | false | Flags if the video should play repeatedly. |
| data-background-video-muted | false | Flags if the audio should be muted. |
| data-background-size | cover | Use `cover` for full screen and some cropping or `contain` for letterboxing. |
| data-background-opacity | 1 | Opacity of the background video on a 0-1 scale. 0 is transparent and 1 is fully opaque. |
```html
<section data-background-video="https://s3.amazonaws.com/static.slid.es/site/homepage/v1/homepage-video-editor.mp4,https://s3.amazonaws.com/static.slid.es/site/homepage/v1/homepage-video-editor.webm" data-background-video-loop data-background-video-muted>
<h2>Video</h2>
</section>
```
#### Iframe Backgrounds
Embeds a web page as a slide background that covers 100% of the reveal.js width and height. The iframe is in the background layer, behind your slides, and as such it's not possible to interact with it by default. To make your background interactive, you can add the `data-background-interactive` attribute.
```html
<section data-background-iframe="https://slides.com" data-background-interactive>
<h2>Iframe</h2>
</section>
```
#### Background Transitions