The 9 Content Objects of HTML

A Content Object inserts non-textual information within a Content Block

Vector Image

A Vector Image embeds a scalable graphic resource

The syntax is an svg element with the following attributes and child elements:

Zero or one count for each attribute defined in the SVG namespace.
Zero or one count for each Global Attribute
Zero or more counts for each element defined in the SVG namespace.

<svg></svg>

Raster Image

A Raster Image inserts an unscalable graphic resource

The syntax is a void img element with the following attributes:

One src attribute
Zero or one count for each of the following attributes: alt, crossorigin, decoding, fetchpriority, height loading, referrerpolicy, sizes, srcset, usemap, and width.
One sizes attribute if the srcset attribute has a value that includes a width descriptor
Zero or one sizes attribute with an auto value if the following conditions are met:
- There's no srcset attribute
- The loading attribute has a lazy value
Zero or one ismap if there's an ancestor a element with an href attribute.
Zero or one count for each Global Attribute

<img src="[url]">

Note: Each Raster Image may have a set of alternatives via a picture element or a set of clickable areas via a Map Card

Audio Media

An Audio Media inserts a sound resource

The syntax is an audio element with the following attributes and child elements:

Zero or one count for each of the following attributes: autoplay, controls. crossorigin, muted, loop, preload, and
src.
Zero or one count for each Global Attribute
The following order of elements:
1. Zero or more source elements if there is no src attribute
2. Any order of the following element variants:
  - Zero or one track element with a default attribute and a kind attribute having a captions keyword or a chapters keyword
  - Zero or one track element with a default attribute and a kind attribute having a descriptions keyword
  - Zero or one track element with a default attribute and a kind attribute having a chapters keyword
  - Zero or more track elements
3. Zero or one count for each element allowed in the parent of this audio element. But, it must exclude descendant of each of the following elements: audio and video. Those elements acts as fallback content when the audio element is not supported by a user agent

<audio></audio>

Video Media

A Video Media insert moving images with or without a sound resource

The syntax is a video element with the following attributes and child elements:

Zero or one count for each of the following attributes:
Zero or one count for each of the following attributes: autoplay, controls. crossorigin, height, attributes. loop, muted, playsinline attribute, poster attribute, preload, and
src. width, and
Zero or one count for each Global Attribute
The following order of elements:
1. Zero or more source elements if there is no src attribute
2. Any order of the following element variants:
  - Zero or one track element with a default attribute and a kind attribute having a captions keyword or a chapters keyword
  - Zero or one track element with a default attribute and a kind attribute having a descriptions keyword
  - Zero or one track element with a default attribute and a kind attribute having a chapters keyword
  - Zero or more track elements
3. Zero or more counts for each element allowed in the parent of this video element. But, it must exclude descendant of each of the following elements: audio and video. Those elements acts as fallback content when the audio element is not supported by a user agent

<video></video>

Math Document

A Math Document embed mathematical notations

The syntax is a math element with the following attributes and child elements:

Zero or one count for each attribute defined in the Math namespace.
Zero or one count for each Global Attribute
Zero or more counts for each element defined in the Math namespace.

<math></math>

Web Document

A Web Document inserts a navigable resource

The syntax is an iframe element with the following attributes and child elements:

Zero or one count for each of the following attributes: allow, allowfullscreen, height, loading, referrerpolicy, srcdoc, sandbox, src, and width.
Zero or one count for each Global Attribute

<iframe></iframe>

General Document

A General Document inserts other document types but as image if not supported by the user agent

An Object Document relates a resource other than a Raster Image, an Audio Media, a Video Media, or a Web Document

The syntax is an object element with the following attributes and child elements:

One data attribute
Zero or one count for each of the following attributes: form, height name, type, and width.
Zero or one count for each Global Attribute
Zero or one count for each element allowed in the parent of this object element

<object data="[URL]"></object>

Embed Medium

An Embed Medium provides an integration point for plugins to insert a document

The syntax is an embed element with the following attributes:

Zero or one count for each of the following attributes: height, src, type, and width.
Zero or one count for each Global Attribute

<embed>

Utilities

A Content Object may use one or more of the following utility contents

Text Track

A Text Track inserts a moving text as an alternative for sounds in an Audio Media or in a Video Media

The syntax is a track element with the following elements and attributes:

One of the following parent elements: audio, or video
One src attribute
Zero or one count for each of the following attributes: default, kind,
label, and srclang.
One srclang attribute if the kind attribute has the subtitles keyword.
Zero or one count for each Global Attribute

<audio>
  <track src="[URL]">
</audio>

<!-- or -->

<video>
  <track src="[URL]">
</video>

Picture Wrapper

A Picture Wrapper provide alternatives for a Raster Image

The syntax is a picture element with the following attributes and child elements:

Zero or one count for each Global Attribute
The following order of child elements, optionally intermixed with script-supporting content:
1. Zero or more source elements
2. One img element

<picture>
  <img src="">
</picture>

Source Component

A Source Component specifies an alternative Raster Image, Audio Media, or Video Media.

The syntax is a source element with the following attributes:

One src attribute if the parent element is an Audio Media or a Video Media
Zero or one count for each of the following attributes. But, one or both if the parent is a Picture Container and it has a sibling Source Component or Raster Image with a srcset attribute
- type attribute
- media attribute
One srcset attribute if the parent is a Picture Container
Zero or one count for each of the following attributes if the parent is a Picture Container
- width attribute
- height attribute
One sizes attribute if all of the following conditions are met. But, optional, if only the first option is met.
1. The srcset attribute has a value that includes a width descriptor
2. The sibling img element does not allow the following auto-sizing attributes and values:
  - One loading attribute with a lazy value
  - One sizes attribute with an "auto" value or starts with an "auto, " value

<picture>
  <source srcset="[IMS]">
</picture>

<audio>
  <source src="[URL]">
</audio>

<video>
  <source src="[URL]">
</video>