<link>: The External Resource Link element
The <link>
HTML element specifies relationships between the current document and an external resource.
This element is most commonly used to link to stylesheets, but is also used to establish site icons (both "favicon" style icons and icons for the home screen and apps on mobile devices) among other things.
Try it
To link an external stylesheet, you'd include a <link>
element inside your <head>
like this:
html
<link href="main.css" rel="stylesheet" />
This simple example provides the path to the stylesheet inside an href
attribute, and a rel
attribute with a value of stylesheet
. The rel
stands for "relationship", and is one of the key features of the <link>
element — the value denotes how the item being linked to is related to the containing document.
There are a number of other common types you'll come across. For example, a link to the site's favicon:
html
<link rel="icon" href="favicon.ico" />
There are a number of other icon rel
values, mainly used to indicate special icon types for use on various mobile platforms, e.g.:
html
<link
rel="apple-touch-icon-precomposed"
sizes="114x114"
href="apple-icon-114.png"
type="image/png" />
The sizes
attribute indicates the icon size, while the type
contains the MIME type of the resource being linked.
These provide useful hints to allow the browser to choose the most appropriate icon available.
You can also provide a media type or query inside a media
attribute; this resource will then only be loaded if the media condition is true. For example:
html
<link href="print.css" rel="stylesheet" media="print" />
<link
href="mobile.css"
rel="stylesheet"
media="screen and (max-width: 600px)" />
Some interesting new performance and security features have been added to the <link>
element too. Take this example:
html
<link
rel="preload"
href="myFont.woff2"
as="font"
type="font/woff2"
crossorigin="anonymous" />
A rel
value of preload
indicates that the browser should preload this resource (see rel="preload"
for more details), with the as
attribute indicating the specific class of content being fetched.
The crossorigin
attribute indicates whether the resource should be fetched with a CORS request.
Other usage notes:
-
A
<link>
element can occur either in the<head>
or<body>
element, depending on whether it has a link type that is body-ok. For example, thestylesheet
link type is body-ok, and therefore<link rel="stylesheet">
is permitted in the body. However, this isn't a good practice to follow; it makes more sense to separate your<link>
elements from your body content, putting them in the<head>
. -
When using
<link>
to establish a favicon for a site, and your site uses a Content Security Policy (CSP) to enhance its security, the policy applies to the favicon. If you encounter problems with the favicon not loading, verify that theContent-Security-Policy
header'simg-src
directive is not preventing access to it. - The HTML and XHTML specifications define event handlers for the
<link>
element, but it is unclear how they would be used. - Under XHTML 1.0, void elements such as
<link>
require a trailing slash:<link />
. - WebTV supports the use of the value
next
forrel
to preload the next page in a document series.
Attributes
This element includes the global attributes.
as
-
This attribute is required when
rel="preload"
has been set on the<link>
element, optional whenrel="modulepreload"
has been set, and otherwise should not be used. It specifies the type of content being loaded by the<link>
, which is necessary for request matching, application of correct content security policy, and setting of correctAccept
request header.Furthermore,
rel="preload"
uses this as a signal for request prioritization. The table below lists the valid values for this attribute and the elements or resources they apply to.Value Applies To audio <audio>
elementsdocument <iframe>
and<frame>
elementsembed <embed>
elementsfetch fetch, XHR
Note: This value also requires
<link>
to contain the crossorigin attribute.font CSS @font-face image <img>
and<picture>
elements with srcset or imageset attributes, SVG<image>
elements, CSS*-image
rulesobject <object>
elementsscript <script>
elements, WorkerimportScripts
style <link rel=stylesheet>
elements, CSS@import
track <track>
elementsvideo <video>
elementsworker Worker, SharedWorker crossorigin
-
This enumerated attribute indicates whether CORS must be used when fetching the resource. CORS-enabled images can be reused in the
<canvas>
element without being tainted. The allowed values are:anonymous
-
A cross-origin request (i.e. with an
Origin
HTTP header) is performed, but no credential is sent (i.e. no cookie, X.509 certificate, or HTTP Basic authentication). If the server does not give credentials to the origin site (by not setting theAccess-Control-Allow-Origin
HTTP header) the resource will be tainted and its usage restricted. use-credentials
-
A cross-origin request (i.e. with an
Origin
HTTP header) is performed along with a credential sent (i.e. a cookie, certificate, and/or HTTP Basic authentication is performed). If the server does not give credentials to the origin site (throughAccess-Control-Allow-Credentials
HTTP header), the resource will be tainted and its usage restricted.
If the attribute is not present, the resource is fetched without a CORS request (i.e. without sending the
Origin
HTTP header), preventing its non-tainted usage. If invalid, it is handled as if the enumerated keyword anonymous was used. See CORS settings attributes for additional information. disabled
Non-standard-
For
rel="stylesheet"
only, thedisabled
Boolean attribute indicates whether the described stylesheet should be loaded and applied to the document. Ifdisabled
is specified in the HTML when it is loaded, the stylesheet will not be loaded during page load. Instead, the stylesheet will be loaded on-demand, if and when thedisabled
attribute is changed tofalse
or removed.Setting the
disabled
property in the DOM causes the stylesheet to be removed from the document'sDocument.styleSheets
list. fetchpriority
Experimental-
Provides a hint of the relative priority to use when fetching a preloaded resource. Allowed values:
high
-
Signals a high-priority fetch relative to other resources of the same type.
low
-
Signals a low-priority fetch relative to other resources of the same type.
auto
-
Default: Signals automatic determination of fetch priority relative to other resources of the same type.
href
-
This attribute specifies the URL of the linked resource. A URL can be absolute or relative.
hreflang
-
This attribute indicates the language of the linked resource. It is purely advisory. Allowed values are specified by RFC 5646: Tags for Identifying Languages (also known as BCP 47). Use this attribute only if the
href
attribute is present. imagesizes
-
For
rel="preload"
andas="image"
only, theimagesizes
attribute is a sizes attribute that indicates to preload the appropriate resource used by animg
element with corresponding values for itssrcset
andsizes
attributes. imagesrcset
-
For
rel="preload"
andas="image"
only, theimagesrcset
attribute is a sourceset attribute that indicates to preload the appropriate resource used by animg
element with corresponding values for itssrcset
andsizes
attributes. integrity
-
Contains inline metadata — a base64-encoded cryptographic hash of the resource (file) you're telling the browser to fetch. The browser can use this to verify that the fetched resource has been delivered free of unexpected manipulation. See Subresource Integrity.
media
-
This attribute specifies the media that the linked resource applies to. Its value must be a media type / media query. This attribute is mainly useful when linking to external stylesheets — it allows the user agent to pick the best adapted one for the device it runs on.
Note:
-
In HTML 4, this can only be a simple white-space-separated list of media description literals, i.e., media types and groups, where defined and allowed as values for this attribute, such as
print
,screen
,aural
,braille
. HTML5 extended this to any kind of media queries, which are a superset of the allowed values of HTML 4. - Browsers not supporting CSS Media Queries won't necessarily recognize the adequate link; do not forget to set fallback links, the restricted set of media queries defined in HTML 4.
-
In HTML 4, this can only be a simple white-space-separated list of media description literals, i.e., media types and groups, where defined and allowed as values for this attribute, such as
prefetch
Secure context Experimental-
Identifies a resource that might be required by the next navigation and that the user agent should retrieve it. This allows the user agent to respond faster when the resource is requested in the future.
referrerpolicy
-
A string indicating which referrer to use when fetching the resource:
no-referrer
means that theReferer
header will not be sent.-
no-referrer-when-downgrade
means that noReferer
header will be sent when navigating to an origin without TLS (HTTPS). This is a user agent's default behavior, if no policy is otherwise specified. origin
means that the referrer will be the origin of the page, which is roughly the scheme, the host, and the port.origin-when-cross-origin
means that navigating to other origins will be limited to the scheme, the host, and the port, while navigating on the same origin will include the referrer's path.-
unsafe-url
means that the referrer will include the origin and the path (but not the fragment, password, or username). This case is unsafe because it can leak origins and paths from TLS-protected resources to insecure origins.
rel
-
This attribute names a relationship of the linked document to the current document. The attribute must be a space-separated list of link type values.
sizes
Experimental-
This attribute defines the sizes of the icons for visual media contained in the resource. It must be present only if the
rel
contains a value oficon
or a non-standard type such as Apple'sapple-touch-icon
. It may have the following values:any
, meaning that the icon can be scaled to any size as it is in a vector format, likeimage/svg+xml
.- a white-space separated list of sizes, each in the format
<width in pixels>x<height in pixels>
or<width in pixels>X<height in pixels>
. Each of these sizes must be contained in the resource.
Note: Most icon formats are only able to store one single icon; therefore, most of the time, the
sizes
attribute contains only one entry. MS's ICO format does, as well as Apple's ICNS. ICO is more ubiquitous, so you should use this format if cross-browser support is a concern (especially for old IE versions). title
-
The
title
attribute has special semantics on the<link>
element. When used on a<link rel="stylesheet">
it defines a default or an alternate stylesheet. type
-
This attribute is used to define the type of the content linked to. The value of the attribute should be a MIME type such as text/html, text/css, and so on. The common use of this attribute is to define the type of stylesheet being referenced (such as text/css), but given that CSS is the only stylesheet language used on the web, not only is it possible to omit the
type
attribute, but is actually now recommended practice. It is also used onrel="preload"
link types, to make sure the browser only downloads file types that it supports. blocking
Experimental-
This attribute explicitly indicates that certain operations should be blocked on the fetching of an external resource. The operations that are to be blocked must be a space-separated list of blocking attributes listed below.
render
: The rendering of content on the screen is blocked.
Non-standard attributes
methods
Non-standard Deprecated-
The value of this attribute provides information about the functions that might be performed on an object. The values generally are given by the HTTP protocol when it is used, but it might (for similar reasons as for the title attribute) be useful to include advisory information in advance in the link. For example, the browser might choose a different rendering of a link as a function of the methods specified; something that is searchable might get a different icon, or an outside link might render with an indication of leaving the current site. This attribute is not well understood nor supported, even by the defining browser, Internet Explorer 4.
target
Deprecated-
Defines the frame or window name that has the defined linking relationship or that will show the rendering of any linked resource.
Obsolete attributes
charset
Deprecated-
This attribute defines the character encoding of the linked resource. The value is a space- and/or comma-delimited list of character sets as defined in RFC 2045. The default value is
iso-8859-1
.Note: To produce the same effect as this obsolete attribute, use the
Content-Type
HTTP header on the linked resource. rev
Deprecated-
The value of this attribute shows the relationship of the current document to the linked document, as defined by the
href
attribute. The attribute thus defines the reverse relationship compared to the value of therel
attribute. Link type values for the attribute are similar to the possible values forrel
.Note: Instead of
rev
, you should use therel
attribute with the opposite link type value. For example, to establish the reverse link formade
, specifyauthor
. Also, this attribute doesn't stand for "revision" and must not be used with a version number, even though many sites misuse it in this way.
Examples
Including a stylesheet
To include a stylesheet in a page, use the following syntax:
html
<link href="style.css" rel="stylesheet" />
Providing alternative stylesheets
You can also specify alternative style sheets.
The user can choose which style sheet to use by choosing it from the View > Page Style menu. This provides a way for users to see multiple versions of a page.
html
<link href="default.css" rel="stylesheet" title="Default Style" />
<link href="fancy.css" rel="alternate stylesheet" title="Fancy" />
<link href="basic.css" rel="alternate stylesheet" title="Basic" />
Providing icons for different usage contexts
You can include links to several icons on the same page, and the browser will choose which one works best for its particular context using the rel
and sizes
values as hints.
html
<!-- third-generation iPad with high-resolution Retina display: -->
<link
rel="apple-touch-icon-precomposed"
sizes="144x144"
href="favicon144.png" />
<!-- iPhone with high-resolution Retina display: -->
<link
rel="apple-touch-icon-precomposed"
sizes="114x114"
href="favicon114.png" />
<!-- first- and second-generation iPad: -->
<link rel="apple-touch-icon-precomposed" sizes="72x72" href="favicon72.png" />
<!-- non-Retina iPhone, iPod Touch, and Android 2.1+ devices: -->
<link rel="apple-touch-icon-precomposed" href="favicon57.png" />
<!-- basic favicon -->
<link rel="icon" href="favicon32.png" />
Conditionally loading resources with media queries
You can provide a media type or query inside a media
attribute;
this resource will then only be loaded if the media condition is true. For example:
html
<link href="print.css" rel="stylesheet" media="print" />
<link href="mobile.css" rel="stylesheet" media="all" />
<link
href="desktop.css"
rel="stylesheet"
media="screen and (min-width: 600px)" />
<link
href="highres.css"
rel="stylesheet"
media="screen and (min-resolution: 300dpi)" />
Stylesheet load events
You can determine when a style sheet has been loaded by watching for a load
event to fire on it; similarly, you can detect if an error has occurred while processing a style sheet by watching for an error
event:
html
<script>
const stylesheet = document.querySelector("#my-stylesheet");
stylesheet.onload = () => {
// Do something interesting; the sheet has been loaded
};
stylesheet.onerror = () => {
console.log("An error occurred loading the stylesheet!");
};
</script>
<link rel="stylesheet" href="mystylesheet.css" id="my-stylesheet" />
Note: The load
event fires once the stylesheet and all of its imported content has been loaded and parsed, and immediately before the styles start being applied to the content.
Preload examples
You can find a number of <link rel="preload">
examples in Preloading content with rel="preload"
.
Blocking rendering till a resource is fetched
You can include render
token inside a blocking
attribute;
the rendering of the page will be blocked till the resource is fetched. For example:
html
<link blocking="render" href="critical-font.woff2" as="font" />
Technical summary
Content categories |
Metadata content.
If itemprop is present:
Flow content and
phrasing content.
|
---|---|
Permitted content | None; it is a void 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 | Any element that accepts metadata elements. If itemprop is present: any element that accepts phrasing content. |
Implicit ARIA role | link with href attribute |
Permitted ARIA roles | No role permitted |
DOM interface | HTMLLinkElement |
Specifications
Specification |
---|
HTML Standard # the-link-element |
Browser compatibility
BCD tables only load in the browser
See also
Link
HTTP header