The 30 Content Metas of HTML

A Content Meta relates an information about the web document to user agents

Each Content Meta must be declared within the Head Container and optionally via a NoScript Container

AppName Meta

The AppName Meta names the application in a document.

The syntax is one void meta element per document with the following attributes:

One name attribute with the application-name value
One content attribute
Zero or one count for each Global Attribute

<meta name="application-name" content="[value]">

Canonical Meta

A Canonical Meta names the original document to the current (duplicate) document

The syntax is a one void link element per document with the following attributes:

One rel attribute with the canonical keyword.
One href attribute
Zero or one count for each of the following attributes:
Zero or one count for the title attribute and each other Global Attribute

<link rel="canonical" href="[resource-url]">

Title Meta

The Title Meta elaborates the document name.

A document must have a Title Meta, except for each of the following cases:

The document is an iframe element with a srcdoc attribute
The title information is available from a higher-level protocol

The syntax is one title element per document with the following attributes and content:

Zero or one count for each Global Attribute
A non-empty text content

<title> [non-empty text] </title>

Description Meta

The Description Meta describes the document.

The syntax is a one void meta element per document with the following attributes:

One name attribute with the description value
One content attribute
Zero or one count for each Global Attribute

<meta name="description" content="[value]">

Keywords Meta

A Keywords Meta identifies the document with a set of keywords.

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

One name attribute with the keywords value
One content attribute
Zero or one count for each Global Attribute

<meta name="keywords" content="[value]">

Author Meta

An Author Meta names the author of a document.

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

One name attribute with the author value
One content attribute
Zero or one count for each Global Attribute

<meta name="author" content="[value]">

Icon Meta

An Icon Meta identifies the document with a graphic resource.

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

One rel attribute with the icon keyword
One href attribute
Zero or one count for each of the following attributes:
Zero or one count for the title attribute and each other Global Attribute

<link rel="icon" href="[resource-url]">

Theme Meta

A Theme Meta relates the color to customize the interface of the user agent.

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

One name attribute with the theme-color value
One content attribute
Zero or one count for each Global Attribute

<meta name="theme-color" content="[value]">

Scheme Meta

The Scheme Meta relates the color scheme to use as default for a web document.

The syntax is one void meta element per document with the following attributes:

One name attribute with the color-scheme value
One content attribute
Zero or one count for each Global Attribute

<meta name="color-scheme" content="[value]">

Translation Meta

A Translation Meta specifies a version of the current document in another language.

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

One rel attribute with the alternate keyword
One href attribute
One hreflang attribute with a language different from that of the document
Zero or one count for each of the following attributes:
- media
- type
Zero or one count for the title attribute and each other Global Attribute

<link rel="alternate" hreflang="[not-document-language]" href="[resource-url]">

Repurposing Meta

A Repurposing Meta specifies a version of the current document in another format.

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

One rel attribute with the alternate keyword
One href attribute
One type attribute without the application/rss+xml value or the application/atom+xml value.
Zero or one count for each of the following attributes:
- hreflang
- media
Zero or one count for the title attribute and each other Global Attribute

<link rel="alternate" href="[URL]" type="[valid-MIME-TYPE]">

Generator Meta

A Generator Meta specifies the name of a software that generates a part or the whole of a web document.

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

One name attribute with the generator value
One content attribute
Zero or one count for each Global Attribute

<meta name="generator" content="[value]">

Pingback Meta

A Pingback Meta relates a server resource to handle pingbacks to a web document

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

One rel attribute with the pingback keyword
One href attribute
Zero or one count for each of the following attributes:
Zero or one count for the title attribute and each other Global Attribute

<link rel="pingback" href="[url]">

Feed Meta

A Feed Meta relates an external resource to syndicate the contents of a web document to aggregators

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

One rel attribute with the alternate keyword
One href attribute
One type attribute with a MIME Type value but not the following keywords: application/rss+xml and application/atom+xml.
Zero or one count for each of the following attributes:
- hreflang
- media
Zero or one count for the title attribute and each other Global Attribute

<link rel="alternate" type="application/rss+xml" href="[resource-url]">
<!-- or -->
<link rel="alternate" type="application/atom+xml" href="[resource-url]">

Referrer Meta

A Referrer Meta specifies the default referrer policy of a web document.

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

One name attribute with the referrer value
One content attribute
Zero or one count for each Global Attribute

<meta name="referrer" content="[value]">

Charset Meta

The Charset Meta specifies the character encoding for a web document.

The syntax is one void meta element per document with either of the following attributes:

One charset attribute with the utf-8 value
Both of the following attributes:
- http-equiv attribute with the content-type value
- content attribute with the "text/html; charset=utf-8" value

<meta charset="utf-8">

<!-- or -->

<meta http-equiv="content-type" content="text/html; charset=utf-8">

URL Meta

The URL Meta specifies a prefix for all non-schemed URLs in a web document.

This meta must precede elements with attributes that accept URLs.

The syntax is one void base element per document with the following attributes:

Zero or one href attribute
Zero or one count for each Global Attribute

<base href="[URL]">

Target Meta

The Target Meta specifies the default opening context for all URLs in a web document.

This Meta must precede elements that represent hyperlinks

The syntax is one void base element per document with the following attributes:

Zero or one target attribute
Zero or one count for each Global Attribute

<base href="[navigable-name-or-keyword]">

Security Meta

The Security Meta specifies a policy to secure the content of a web document.

The syntax is one void meta element per document with the following attributes:

One http-equiv attribute with the content-security-policy value
One content attribute
Zero or one count for each Global Attribute

<meta http-equiv="content-security-policy" content="[value]">

Timeout Meta

The Timeout Meta specifies the time to redirect a web document.

The syntax is one void meta element per document with the following attributes:

One http-equiv attribute with the refresh value
One content attribute
Zero or one count for each Global Attribute

<meta http-equiv="refresh" content="[value]">

Manifest Meta

A Manifest Meta specifies a JSON resource that provides information about the web application in a web document.

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

One rel attribute with a manifest keyword. And, an optional preload keyword
One href attribute
One as attribute with a manifest value if the preload keyword is in the rel attribute.
Zero or one count for each of the following attributes:
Zero or one integrity attribute if the preload keyword is in the rel attribute
Zero or one count for each Global Attribute

<link rel="manifest" href="[url]">

Next Meta

A Next Meta specifies a resource that is next in sequence to the current document.

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

One rel attribute with the next keyword
One href attribute
Zero or one count for each of the following attributes:
Zero or one count for the title attribute and each other Global Attribute

<link rel="next" href="[resource-url]">

Search Meta

A Search Meta relates an external resource to discover the contents of the current document.

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

One rel attribute with the search keyword
One href attribute
Zero or one count for each of the following attributes:
Zero or one count for the title attribute and each other Global Attribute

<link rel="search" href="[resource-url]">

Asset Meta

An Asset Meta relates a resource to be loaded in advance for a document

The syntax is a void link element with the following keywords:

One rel attribute with a preload keyword.
One as attribute with one of the following value: '', audio, audioworklet, document, embed, font, frame, iframe, image, json, manifest, object, paintworklet, report, script, serviceworker, sharedworker, style, track, video, webidentity, worker, or xslt.
One href attribute if value of as attribute is not image
One or both of href and imagesrcset if value of as attribute is image
Zero or one imagesizes attribute if the imagesrscet attribute has a value that includes a width descriptor
One crossorigin if value of as attribute is font otherwise optional
Zero or one count for each of the following attributes: fetchpriority, hreflang, integrity, media, referrerpolicy, type
Zero or one count for each Global Attribute

<link rel="preload" as="[font|image|audio|video|track|object|embed|document]" href="[URL]">

Template Meta

A Template Meta specifies a fragment of an HTML document with optional placeholders

The syntax is a template element with the following attributes and contents:

Zero or one count for each of the following attributes:
- shadowrootmode
- shadowrootdelegatesfocus
Zero or one count for each Global Attribute
Zero or more counts for each Flow Content Element.

<template>

</template>

Stylesheet Meta

A Stylesheet Meta relates a set of CSS Rules for a document.

Each set may be embedded on or externalized to the page. A collection of stylesheets with the same title make up a theme. One theme can be the default.

The syntax for an Embedded Stylesheet is a style element with the following attributes and content:

Zero or one count for each of the following attributes:
- blocking
- media
Zero or one count for the title attribute and each other Global Attribute
A text content that gives a conformant style sheet

<style>
  /* text that is style conformant */
</style>

The syntax for an External Stylesheet is a void link element with the following attributes:

One rel attribute with the stylesheet keyword.
One href attribute
One as attribute with a style value if there's a preload keyword in the rel attribute
Zero or one count for each of the following attributes:
Zero or one count for the title attribute and each other Global Attribute

<link rel="stylesheet" href="[URL]">

The syntax for a default Stylesheet Theme is one void meta element per document with the following attributes:

One http-equiv attribute with the default-style value
One content attribute whose value is the name of a Stylesheet Theme

<meta http-equiv="default-style" content="[text]">

Script Meta

A Script Meta relates a set of JavaScript instructions for a document

The syntax is a script element with the following attributes and content:

Zero or one count for each of the following attributes:
Zero or one count for each of the following attributes if the type attribute is ommitted, an empty string, a Javascript Mime Type, or a module
- src
- referrerpolicy
- crossorigin
- nomodule if type is not module
Zero or one count for each of the following attributes if there's a src attribute:
- async
- integrity
- defer if type is not module
Zero or one count for each Global Attribute
An optional text content matching script content restrictions and conforming to a script documentation if there's a src attribute
A text content matching script content restrictions and conforming to the value of the type attribute if there's no src attribute

<script></script>

Data Meta

A Data Meta relates data blocks for document scripts

The syntax is a script element with the following attributes and content:

One type attribute with a MIME Type value other than the text/javascript value
Zero or One blocking attribute
A text content that satisfy the following 2 conditions:
- matches script content restrictions
- conforms to the value of the type attribute

<script type="[mime-type-but-not-text/javascript]"></script>

Link Meta

A Custom Link Meta specifies a non-standard metadata keyword whose value must be a URL to a resource

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

One rel attribute but it must have an extension link type keyword
One href attribute
Zero or one for the following attributes if the extension link type is an external resource link: crossorigin fetchpriority, and referrerpolicy
Zero or one count for each of the following attributes:
hreflang, media, and type
Zero or one color attribute if rel attribute has a mask-icon
Zero or one count for each Global Attribute

<link rel="[extension-link-type-keyword]" href="[URL]">

Text Meta

A Text Meta specifies a non-standard metadata keyword whose value must not be a URL to a resource

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

One name attribute whose value must be a Meta Name Extension
One content attribute
Zero or one count for each Global Attribute

<meta name="[meta-name-extension]" value="[value]">

Appendix

The following utilities applies to Content Metas

Head Container

The Head Container specifies a collection of Content Metas to User Agents for processing

The syntax is an head element with the following attributes and contents:

Zero or one count for each Global Attribute
Zero or more counts for most Content Metas

<head>
  <!-- Content Metas -->
</head>

Noscript Container

A Noscript Container in a Meta Container relates Content Metas to User Agents that doesn't support scripting functionality on a web document.

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

Zero or one count for each Global Attribute
Zero or more counts for each Content Metas except the following: Title Meta, Url Meta, Target Meta, Template Meta, and loaded (not preloaded) Script Meta

<noscript>

</noscript>

Slot Wrapper

A Template Placeholder specifies a replaceable part within a reusable markup

The syntax is a slot element with the following attributes and contents:

Zero or one slot attribute
Zero or one count for each Global Attribute
Zero or one count for each element allowed in the parent element

<slot></slot>