Baseline Widely available *
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.
<link href="/shared-assets/misc/link-element-example.css" rel="stylesheet" />
<p>This text will be red as defined in the external stylesheet.</p>
<p style="color: blue">
The <code>style</code> attribute can override it, though.
</p>
To link an external stylesheet, you'd include a <link> element inside your <head> like this:
<link href="main.css" rel="stylesheet" />
This 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 â 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:
<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.:
<link
rel="apple-touch-icon"
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:
<link href="print.css" rel="stylesheet" media="print" />
<link href="mobile.css" rel="stylesheet" media="screen and (width <= 600px)" />
Some interesting new performance and security features have been added to the <link> element too. Take this example:
<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:
<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, the stylesheet 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>.<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 the Content-Security-Policy header's img-src directive is not preventing access to it.<link> element, but it is unclear how they would be used.<link> require a trailing slash: <link />.next for rel to preload the next page in a document series.This element includes the global attributes.
as
This attribute is required when rel="preload" has been set on the <link> element, optional when rel="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 correct Accept 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.
<audio> elements document <iframe> and <frame> elements embed <embed> elements fetch
fetch, XHR
Note: This value also requires <link> to contain the crossorigin attribute, see CORS-enabled fetches.
CSS @font-face
Note: This value also requires <link> to contain the crossorigin attribute, see CORS-enabled fetches.
<img> and <picture> elements with srcset or imageset attributes, SVG <image> elements, CSS *-image rules object <object> elements script <script> elements, Worker importScripts style <link rel=stylesheet> elements, CSS @import track <track> elements video <video> elements worker Worker, SharedWorker
blocking
This attribute explicitly indicates that certain operations should be blocked until specific conditions are met. It must only be used when the rel attribute contains the expect or stylesheet keywords. With rel="expect", it indicates that operations should be blocked until a specific DOM node has been parsed. With rel="stylesheet", it indicates that operations should be blocked until an external stylesheet and its critical subresources have been fetched and applied to the document. The operations that are to be blocked must be a space-separated list of blocking tokens listed below. Currently there is only one token:
render: The rendering of content on the screen is blocked.Note: Only link elements in the document's <head> can possibly block rendering. By default, a link element with rel="stylesheet" in the <head> blocks rendering when the browser discovers it during parsing. If such a link element is added dynamically via script, you must additionally set blocking = "render" for it to block rendering.
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 the Access-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 (through Access-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
For rel="stylesheet" only, the disabled Boolean attribute indicates whether the described stylesheet should be loaded and applied to the document. If disabled 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 the disabled attribute is changed to false or removed.
Setting the disabled property in the DOM causes the stylesheet to be removed from the document's Document.styleSheets list.
fetchpriority
Provides a hint of the relative priority to use when fetching a resource of a particular type. Allowed values:
high
Fetch the resource at a high priority relative to other resources of the same type.
low
Fetch the resource at a low priority relative to other resources of the same type.
auto
Don't set a preference for the fetch priority. This is the default. It is used if no value or an invalid value is set.
See HTMLLinkElement.fetchPriority for more information.
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" and as="image" only, the imagesizes attribute has similar syntax and semantics as the sizes attribute that indicates to preload the appropriate resource used by an img element with corresponding values for its srcset and sizes attributes.
imagesrcset
For rel="preload" and as="image" only, the imagesrcset attribute has similar syntax and semantics as the srcset attribute that indicates to preload the appropriate resource used by an img element with corresponding values for its srcset and sizes attributes.
integrity
Contains inline metadata â 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 without unexpected manipulation. The attribute must only be specified when the rel attribute is specified to stylesheet, preload, or modulepreload. 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 â it allows the user agent to pick the best adapted one for the device it runs on.
referrerpolicy
A string indicating which referrer to use when fetching the resource:
no-referrer means that the Referer header will not be sent.no-referrer-when-downgrade means that no Referer 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
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 of icon or a non-standard type such as Apple's apple-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, like image/svg+xml.<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. Microsoft's ICO format and Apple's ICNS format can store multiple icon sizes in a single file. ICO has better browser support, so you should use this format if cross-browser support is a concern.
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 on rel="preload" link types, to make sure the browser only downloads file types that it supports.
target Deprecated
Defines the frame or window name that has the defined linking relationship or that will show the rendering of any linked resource.
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 the rel attribute. Link type values for the attribute are similar to the possible values for rel.
Note: Instead of rev, you should use the rel attribute with the opposite link type value. For example, to establish the reverse link for made, specify author. 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.
To include a stylesheet in a page, use the following syntax:
<link href="style.css" rel="stylesheet" />
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.
<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" />
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.
<!-- iPad Pro with high-resolution Retina display: -->
<link
rel="apple-touch-icon"
sizes="167x167"
href="/apple-touch-icon-167x167.png" />
<!-- 3x resolution iPhone: -->
<link
rel="apple-touch-icon"
sizes="180x180"
href="/apple-touch-icon-180x180.png" />
<!-- non-Retina iPad, iPad mini, etc.: -->
<link
rel="apple-touch-icon"
sizes="152x152"
href="/apple-touch-icon-152x152.png" />
<!-- 2x resolution iPhone and other devices: -->
<link rel="apple-touch-icon" href="/apple-touch-icon-120x120.png" />
<!-- basic favicon -->
<link rel="icon" href="/favicon.ico" />
For information about what sizes to choose for Apple icons, see Apple's documentation on configuring web applications and the referenced Apple human interface guidelines. Usually, it is sufficient to provide a large image, such as 192x192, and let the browser scale it down as needed, but you may want to provide images with different levels of detail for different sizes, as the Apple design guideline recommends. Providing smaller icons for lower resolutions also saves bandwidth.
It may not be necessary to provide <link> elements at all. For example, browsers automatically request /favicon.ico from the root of a site, and Apple also automatically requests /apple-touch-icon-[size].png, /apple-touch-icon.png, etc. However, providing explicit links protects you against changes to these conventions.
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:
<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 (width >= 600px)" />
<link
href="highres.css"
rel="stylesheet"
media="screen and (resolution >= 300dpi)" />
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:
<link rel="stylesheet" href="mystylesheet.css" id="my-stylesheet" />
const stylesheet = document.getElementById("my-stylesheet");
stylesheet.onload = () => {
// Do something interesting; the sheet has been loaded
};
stylesheet.onerror = () => {
console.log("An error occurred loading the 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.
You can find a number of <link rel="preload"> examples in Preloading content with rel="preload".
You can include render token inside a blocking attribute; the rendering of the page will be blocked till the resource and its critical subresources are fetched and applied to the document. For example:
<link blocking="render" rel="stylesheet" href="example.css" crossorigin />
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