HTML Guide
link
elements are used to link to external resources, such as stylesheets, scripts, and icons. Including relevant attributes in the link
element helps provide additional information about the linked resource.
-
rel
: Therel
attribute specifies the relationship between the current document and the linked resource, and can also provide additional information about the type of linked resource. For example, usingrel="stylesheet"
for a linked CSS file orrel="icon"
for a linked favicon. -
itemprop
: If the linked resource is an HTML document or a microdata vocabulary like Schema.org, useitemprop
to specify properties the linked document or vocabulary defines. -
property
: If the linked resource is an RDF resource, useproperty
to provide metadata about the relationship between the current document and the resource being linked.
Example with rel
attribute:
<head>
<link rel="stylesheet" href="styles.css">
<!-- Other meta tags -->
</head>
Example with itemprop
and property
attributes:
<head>
<link itemprop="mentions" href="https://example.com/">
<link property="schema:citation" href="https://example.com/article.html">
<!-- Other meta tags -->
</head>
By adding itemprop
, property
, or rel
as necessary, you can ensure your link
elements provide appropriate context and semantic meaning to your HTML document.
Learn more:
Related W3C validator issues
The error message indicates that the <link> element contains an as attribute, but its rel attribute does not hold the correct value. According to the HTML specification, when using the as attribute, the rel attribute must be set to "preload" or "modulepreload".
Explanation
The as attribute is used to specify the type of content being loaded, which helps the browser to handle it appropriately. To preload resources, you need to specify the rel attribute with the value "preload" (for general resources) or "modulepreload" (specifically for JavaScript modules).
Example with preload:
If you are preloading a stylesheet, the rel attribute should be set to "preload":
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Correct Usage of Link with as Attribute</title>
<link rel="preload" href="styles.css" as="style">
</head>
<body>
<p>Hello, World!</p>
</body>
</html>
Example with modulepreload:
If you are preloading a JavaScript module, the rel attribute should be set to "modulepreload":
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Correct Usage of Link with Modulepreload</title>
<link rel="modulepreload" href="script.js" as="script">
</head>
<body>
<p>Hello, World!</p>
</body>
</html>
A <link> element must include at least one of the attributes href, rel, itemprop, property, or resource.
The <link> element is used to define the relationship between the current document and an external resource, most commonly for linking stylesheets (rel="stylesheet") or providing metadata. According to the HTML specification, at least one of the attributes href, rel, itemprop, property, or resource must be present so the browser or validator knows the purpose of the link.
Correct usage with rel and href:
<link rel="stylesheet" href="styles.css">
Correct usage with property:
<link property="og:image" href="image.png">
There’s an incomplete or incorrectly formed <meta> tag. The <meta> tag in HTML is used to provide metadata about the HTML document. This metadata is typically specified using attributes like charset, content, http-equiv, itemprop, name, and property.
To fix this issue, you need to ensure that your <meta> tags include at least one of these attributes. Here are some examples of properly formed <meta> tags with each of these attributes:
-
Using the charset attribute:
<meta charset="UTF-8">
This specifies the character encoding for the HTML document, which is crucial for displaying text correctly in different languages.
-
Using the content and name attributes:
<meta name="description" content="A brief description of the webpage content.">
This provides a description of the webpage content, which can be used by search engines.
-
Using the http-equiv and content attributes:
<meta http-equiv="refresh" content="30">
This specifies information to be passed to the browser, such as refreshing the page every 30 seconds.
-
Using the property and content attributes:
<meta property="og:title" content="Your Webpage Title">
This is used for Open Graph meta tags, which improve the appearance of shared content on social media platforms.
Correct Usage Example
Here’s an example of an HTML document with a properly formed set of <meta> tags:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta name="description" content="A brief description of the webpage content.">
<meta http-equiv="refresh" content="30">
<meta property="og:title" content="Your Webpage Title">
<title>Document</title>
</head>
<body>
<!-- Page content goes here -->
</body>
</html>
A <meta> element without a content, itemprop or property attributes has been found in an unexpected place.
Check its attributes and context - depending on the section of the document (<head> or <body>), the <meta> element allows different attributes.
A <meta> element without a itemprop or property attributes has been found in an unexpected place.
While the <meta> element is commonly used within the <head> section of the document, it can also be used within the <body> section, for example in the context of defining microdata, as in this example:
<div itemprop="offers" itemscope itemtype="http://schema.org/Offer">
Price: $<span itemprop="price">1.00</span>
<meta itemprop="priceCurrency" content="USD" />
</div>
When used within the <body> section, the <meta> element is required to have a itemprop or property, and a content attribute, and it can’t have a http-equiv or charset attribute.
A common cause for this issue is including a <meta> element that was intended for the <head> section (for example one containing a http-equiv attribute in the <body> , for example:
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<form>
...
</form>
A link element is invalid unless it contains at least one of the href or imagesrcset attributes.
The link element is used to define relationships between the current document and external resources, most commonly stylesheets. According to the HTML standard, a link must have either an href attribute, which points to the resource, or an imagesrcset attribute for responsive icons. If both are missing, the validator throws an error. This ensures that the link actually references a resource, otherwise it serves no functional purpose.
Correct usage:
With an href (for stylesheets, icons, etc.)
<link rel="stylesheet" href="styles.css">
With imagesrcset (for responsive icons)
<link rel="preload" as="image" type="image/png" imagesrcset="icon-1x.png 1x, icon-2x.png 2x">
A <link> element has been found in an invalid body context. Check the attributes of the <link> element and ensure it’s not within the <body> section.
If the element is within the <head> section, it may have been interpreted as a body context depending on previous elements. For example, while this <link> element is valid per se and is in the <head> section, it is deemed invalid because the previous <img> element made the validator consider it a body context:
<!DOCTYPE html>
<html lang="">
<head>
<title>Test</title>
<img src="photo.jpg" alt="A smiling cat" />
<link rel="canonical" href="https://example.com/" />
</head>
<body>
<p>Some content</p>
</body>
</html>
If we fix that document and move the <img> tag within the body, the issue raised about <meta> disappears because it’s now in a valid context:
<!DOCTYPE html>
<html lang="">
<head>
<title>Test</title>
<link rel="canonical" href="https://example.com/" />
</head>
<body>
<p>Some content</p>
<img src="photo.jpg" alt="A smiling cat" />
</body>
</html>
A <link> element that is using the preload value in the rel attribute is missing the as attribute, used to indicate the type of the resource.
The preload value of the <link> element’s rel attribute lets you declare fetch requests in the HTML’s <head>, specifying resources that your page will need very soon, which you want to start loading early in the page lifecycle, before browsers’ main rendering machinery kicks in. This ensures they are available earlier and are less likely to block the page’s render, improving performance.
The as attribute 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.
An illegal character has been found for the “href” attribute on the “link” element.
To fix this issue, find the “link” element in question and make sure that the “href” attribute contains a valid URL without any illegal characters.
Here’s some example HTML code of a link element:
<!DOCTYPE html>
<html>
<head>
<title>My Webpage</title>
<link rel="stylesheet" href="styles/main.css">
</head>
<body>
<h1>Welcome to my webpage!</h1>
<p>Here is some content...</p>
</body>
</html>
In the above example, the link element has a valid href attribute value of styles/main.css. Make sure that your href attribute values don’t contain any illegal characters.
The href attribute on the link element must not be empty.