<meta>: The Document-level Metadata element

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Attributes
Notes
Examples
Accessibility concerns
Specifications
Browser compatibility
See also

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The HTML <meta> element represents metadata that cannot be represented by other HTML meta-related elements, like <base>, <link>, <script>, <style> or <title>.

Content categories	Metadata content. If the `itemprop` attribute is present: flow content, phrasing content.
Permitted content	None, it is an empty element.
Tag omission	As it is a void element, the start tag must be present and the end tag must not be present.
Permitted parents	`<meta charset>`, `<meta http-equiv>`: a `<head>` element. If the `http-equiv` is not an encoding declaration, it can also be inside a `<noscript>` element, itself inside a `<head>` element.
Permitted ARIA roles	None
DOM interface	`HTMLMetaElement`

Attributes

This element includes the global attributes.

Note: the global attribute name has a specific meaning for the <meta> element, and the itemprop attribute must not be set on the same <meta> element that has any existing name, http-equiv or charset attributes.

charset

This attribute declares the page's character encoding. It must contain a standard IANA MIME name for character encodings. Although the standard doesn't request a specific encoding, it suggests:

Authors are encouraged to use UTF-8.
Authors should not use ASCII-incompatible encodings to avoid security risk: browsers not supporting them may interpret harmful content as HTML. This happens with the JIS_C6226-1983, JIS_X0212-1990, HZ-GB-2312, JOHAB, the ISO-2022 family and the EBCDIC family.

Note: ASCII-incompatible encodings are those that don't map the 8-bit code points 0x20 to 0x7E to the 0x0020 to 0x007E Unicode code points)

Authors must not use CESU-8, UTF-7, BOCU-1 and/or SCSU as cross-site scripting attacks with these encodings have been demonstrated.
Authors should not use UTF-32 because not all HTML5 encoding algorithms can distinguish it from UTF-16.

Notes:

The declared character encoding must match the one the page was saved with to avoid garbled characters and security holes.
The <meta> element declaring the encoding must be inside the <head> element and within the first 1024 bytes of the HTML as some browsers only look at those bytes before choosing an encoding.
This <meta> element is only one part of the algorithm to determine a page's character set. The Content-Type header and any Byte-Order Marks override this element.
It is strongly recommended to define the character encoding. If a page's encoding is undefined, cross-scripting techniques are possible, such as the UTF-7 fallback cross-scripting technique.
The <meta> element with a charset attribute is a synonym for the pre-HTML5 <meta http-equiv="Content-Type" content="text/html; charset=IANAcharset">, where IANAcharset contains the value of the equivalent charset attribute. This syntax is still allowed, although no longer recommended.

content

This attribute contains the value for the http-equiv or name attribute, depending on which is used.

http-equiv

Defines a pragma directive. The attribute is named http-equiv(alent) because all the allowed values are names of particular HTTP headers:

"content-language"
Defines the default language of the page. It can be overridden by the lang attribute on any element.

Warning: Do not use this value, as it is obsolete. Prefer the lang attribute on the <html> element.
"content-security-policy"
Allows page authors to define a content policy for the current page. Content policies mostly specify allowed server origins and script endpoints which help guard against cross-site scripting attacks.
"content-type"
Defines the MIME type of the document, followed by its character encoding. It follows the same syntax as the HTTP content-type entity-header field, but as it is inside a HTML page, most values other than text/html are impossible. Therefore the valid syntax for its content is the string 'text/html' followed by a character set with the following syntax: '; charset=IANAcharset', where IANAcharset is the preferred MIME name for a character set as defined by the IANA.

Warning: Do not use this value, as it is obsolete. Use the charset attribute on the <meta> element.

Note: As <meta> can't change documents' types in XHTML or HTML5's XHTML serialization, never set the MIME type to an XHTML MIME type with <meta>.
"refresh"
This instruction specifies:
- The number of seconds until the page should be reloaded - only if the content attribute contains a positive integer.
- The number of seconds until the page should redirect to another - only if the content attribute contains a positive integer followed by the string ';url=', and a valid URL.
"set-cookie"
Defines a cookie for the page. Its content must follow the syntax defined in the IETF HTTP Cookie Specification.

Warning: Do not use this instruction, as it is obsolete. Use the HTTP header Set-Cookie instead.

name

This attribute defines the name of a piece of document-level metadata. It should not be set if one of the attributes itemprop, http-equiv or charset is also set.

This metadata name is associated with the value contained by the content attribute. The possible values for the name attribute are:

application-name which defines the name of the application running in the web page.
Note:
- Browsers may use this to identify the application. It is different from the <title> element, which usually contain the application name, but may also contain information like the document name or a status.
- Simple web pages shouldn't define an application-name.
author which defines the name of the document's author.
description which contains a short and accurate summary of the content of the page. Several browsers, like Firefox and Opera, use this as the default description of bookmarked pages.
generator which contains the identifier of the software that generated the page.
keywords which contains words relevant to the page's content separated by commas.

referrer which controls the Referer HTTP header attached to requests sent from the document:

Values for the `content` attribute of `<meta name="referrer">`
`no-referrer`	Do not send a HTTP `Referrer` header.
`origin`	Send the origin of the document.
`no-referrer-when-downgrade`	Send the origin as a referrer to URLs as secure as the current page, (https→https), but does not send a referrer to less secure URLs (https→http). This is the default behaviour.
`origin-when-cross-origin`	Send the full URL (stripped of parameters) for same-origin requests, but only send the origin for other cases.
`same-origin`	A referrer will be sent for same-site origins, but cross-origin requests will contain no referrer information.
`strict-origin`	Only send the origin of the document as the referrer to a-priori as-much-secure destination (HTTPS->HTTPS), but don't send it to a less secure destination (HTTPS->HTTP).
`strict-origin-when-cross-origin`	Send a full URL when performing a same-origin request, only send the origin of the document to a-priori as-much-secure destination (HTTPS->HTTPS), and send no header to a less secure destination (HTTPS->HTTP).
`unsafe-URL`	Send the full URL (stripped of parameters) for same-origin or cross-origin requests.

Notes:

Some browsers support the deprecated values of always, default, and never for referrer.
Dynamically inserting <meta name="referrer"> (with document.write or appendChild) makes the referrer behaviour unpredictable.
When several conflicting policies are defined, the no-referrer policy is applied.

This attribute may also have a value taken from the extended list defined on WHATWG Wiki MetaExtensions page. Although none have been formally accepted yet, a few commonly used names are:

creator which defines the name of the creator of the document, such as an organization or institution. If there are more than one, several <meta> elements should be used.
googlebot, a synonym of robots, is only followed by Googlebot (the indexing crawler for Google).
publisher which defines the name of the document's publisher.

robots which defines the behaviour that cooperative crawlers, or "robots", should use with the page. It is a comma-separated list of the values below:

Values for the content of `<meta name="robots">`
Value	Description	Used by
`index`	Allows the robot to index the page (default).	All
`noindex`	Requests the robot to not index the page.	All
`follow`	Allows the robot to follow the links on the page (default).	All
`nofollow`	Requests the robot to not follow the links on the page.	All
`none`	Equivalent to `noindex, nofollow`	Google
`noodp`	Prevents using the Open Directory Project description, if any, as the page description in search engine results.	Google, Yahoo, Bing
`noarchive`	Requests the search engine not to cache the page content.	Google, Yahoo, Bing
`nosnippet`	Prevents displaying any description of the page in search engine results.	Google, Bing
`noimageindex`	Requests this page not to appear as the referring page of an indexed image.	Google
`nocache`	Synonym of `noarchive`.	Bing

Notes:

Only cooperative robots follow these rules. Do not expect to prevent e-mail harvesters with them.
The robot still needs to access the page in order to read these rules. To prevent bandwidth consumption, use a robots.txt file.
If you want to remove a page, noindex will work, but only after the robot visits the page again. Ensure that the robots.txt file is not preventing revisits.
Some values are mutually exclusive, like index and noindex, or follow and nofollow. In these cases the robot's behaviour is undefined and may vary between them.
Some crawler robots, like Google, Yahoo and Bing, support the same values for the HTTP header X-Robots-Tag; this allows non-HTML documents like images to use these rules.

slurp, is a synonym of robots, but only for Slurp - the crawler for Yahoo Search.

viewport, which gives hints about the size of the initial size of the viewport. Used by mobile devices only.

Values for the content of `<meta name="viewport">`
Value	Possible subvalues	Description
`width`	A positive integer number, or the text `device-width`	Defines the pixel width of the viewport that you want the web site to be rendered at.
`height`	A positive integer, or the text `device-height`	Defines the height of the viewport. Not used by any browser.
`initial-scale`	A positive number between `0.0` and `10.0`	Defines the ratio between the device width (`device-width` in portrait mode or `device-height` in landscape mode) and the viewport size.
`maximum-scale`	A positive number between `0.0` and `10.0`	Defines the maximum amount to zoom in. It must be greater or equal to the `minimum-scale` or the behaviour is undefined. Browser settings can ignore this rule and iOS10+ ignores it by default.
`minimum-scale`	A positive number between `0.0` and `10.0`	Defines the minimum zoom level. It must be smaller or equal to the `maximum-scale` or the behaviour is undefined. Browser settings can ignore this rule and iOS10+ ignores it by default.
`user-scalable`	`yes` or `no`	If set to `no`, the user is not able to zoom in the webpage. The default is `yes`. Browser settings can ignore this rule, and iOS10+ ignores it by default.

Specification	Status	Comment
CSS Device Adaptation The definition of '<meta name="viewport">' in that specification.	Working Draft	Non-normatively describes the Viewport META element

Notes

Depending on the attributes set, the kind of metadata can be one of the following:

If name is set, it is document-level metadata, applying to the whole page.
If http-equiv is set, it is a pragma directive — information normally given by the web server about how the web page is served.
If charset is set, it is a charset declaration — the character encoding used by the webpage.
If itemprop is set, it is user-defined metadata — transparent for the user-agent as the semantics of the metadata is user-specific.

Examples

<meta charset="utf-8">

<!-- Redirect page after 3 seconds -->
<meta http-equiv="refresh" content="3;url=https://www.mozilla.org">

Accessibility concerns

Refreshing content

Pages set with a refresh value run the risk of having the time interval being too short. People navigating with the aid of assistive technology such as a screen reader may be unable to read through and understand the page's content before being automatically redirected. The abrupt, unannounced updating of the page content may also be disorienting for people experiencing low vision conditions.

Viewport scaling

Disabling zooming capabilities by setting user-scalable to a value of no prevents people experiencing low vision conditions from being able to read and understand page content.

Specifications

Specification	Status	Comment
Referrer Policy The definition of '<meta name="referrer">' in that specification.	Candidate Recommendation	Defines values and semantics of `<meta name="referrer">`.
HTML Living Standard The definition of '<meta>' in that specification.	Living Standard	Added `itemprop` attribute
HTML5 The definition of '<meta>' in that specification.	Recommendation	Added `charset` attribute
HTML 4.01 Specification The definition of '<meta>' in that specification.	Recommendation

Browser compatibility

The information shown below has been pulled from MDN's Github (https://github.com/mdn/browser-compat-data).

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Edge Mobile	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
Basic support	Chrome Full support Yes	Edge Full support Yes	Firefox Full support 1	IE Full support Yes	Opera Full support Yes	Safari Full support Yes	WebView Android Full support Yes	Chrome Android Full support Yes	Edge Mobile Full support Yes	Firefox Android Full support 4	Opera Android Full support Yes	Safari iOS Full support Yes	Samsung Internet Android Full support Yes
`charset`	Chrome Full support Yes	Edge Full support Yes	Firefox Full support 1	IE Full support Yes	Opera Full support Yes	Safari Full support Yes	WebView Android Full support Yes	Chrome Android Full support Yes	Edge Mobile Full support Yes	Firefox Android Full support 4	Opera Android Full support Yes	Safari iOS Full support Yes	Samsung Internet Android Full support Yes
`content`	Chrome Full support Yes	Edge Full support Yes	Firefox Full support 1	IE Full support Yes	Opera Full support Yes	Safari Full support Yes	WebView Android Full support Yes	Chrome Android Full support Yes	Edge Mobile Full support Yes	Firefox Android Full support 4	Opera Android Full support Yes	Safari iOS Full support Yes	Samsung Internet Android Full support Yes
`http-equiv`	Chrome Full support Yes	Edge Full support Yes	Firefox Full support 1	IE Full support Yes	Opera Full support Yes	Safari Full support Yes	WebView Android Full support Yes	Chrome Android Full support Yes	Edge Mobile Full support Yes	Firefox Android Full support 4	Opera Android Full support Yes	Safari iOS Full support Yes	Samsung Internet Android Full support Yes
`name`	Chrome Full support Yes	Edge Full support Yes	Firefox Full support 1	IE Full support Yes	Opera Full support Yes	Safari Full support Yes	WebView Android Full support Yes	Chrome Android Full support Yes	Edge Mobile Full support Yes	Firefox Android Full support 4	Opera Android Full support Yes	Safari iOS Full support Yes	Samsung Internet Android Full support Yes

Legend

Full support: Full support

Document Tags and Contributors

Những người đóng góp cho trang này: linhtrn21

Cập nhật lần cuối bởi: linhtrn21, 19:53:46, 6 thg 9, 2018

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<meta>: The Document-level Metadata element

Attributes

Notes

Examples

Accessibility concerns

Refreshing content

Viewport scaling

Specifications

Browser compatibility

Legend

See also

Document Tags and Contributors

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