HTML Guides for less than

The href value on the <a> element contains a literal < character, which is not allowed in a URL path.

The URL standard does not allow a raw < anywhere in a URL. Escaping it as < does not help, because the HTML parser turns < back into < before the URL is read. If a path really needs the character, write it as %3C.

A value that starts with part of a tag, such as <div class=, means a template or content filter wrote HTML where a URL belongs. Lazy-loading and video embed plugins can do this when they swap a video URL for placeholder markup without checking whether the URL sits inside an attribute. The first " in that markup closes the href, so the value stops at class= and the browser treats it as a relative path to a page that doesn't exist.

The rest of the injected tag spills into the <a> start tag as broken attributes. That's why the validator usually also reports a stray end tag and a quote in an attribute name for the same link. Those errors go away once the href holds a plain URL.

Other values with a < come from angle brackets copied along with an address, as in <https://www.example.com/> from a plain-text email, or from placeholders like /files/<name>.pdf left in a template. Remove the brackets or fill in the real value.

Invalid example

<a href="<div class="video-embed" data-src="https://www.example.com/embed/abc123"></div>">Watch the video</a>

Valid example

<a href="https://www.example.com/embed/abc123">Watch the video</a>

When the HTML parser reads a tag, it expects a specific sequence: the tag name, then optional attributes (each with a name, optionally followed by = and a value), and finally a closing >. If the parser encounters a < character in a position where it's looking for an attribute name, it means something has gone structurally wrong. The parser interprets the < as the beginning of a new tag, but since it's still inside the current tag's definition, it raises this error.

This issue commonly arises from three scenarios:

1. A stray < character inside a tag — perhaps from a typo or a copy-paste error.
2. A missing > on a previous tag — causing the parser to treat the next tag's < as though it's still part of the previous tag's attributes.
3. Incorrectly nested or overlapping tags — where one element is accidentally placed inside another element's opening tag.

This matters because browsers handle malformed HTML unpredictably. One browser might silently ignore the stray character, while another might drop the entire element or render content incorrectly. Fixing these structural errors ensures consistent rendering across all browsers and improves accessibility, since screen readers and other assistive technologies rely on well-formed markup to interpret page structure.

Examples

Stray < character inside a tag

A common typo where an extra < appears before the closing of a self-closing tag or between attributes:

<!-- ❌ Stray "<" inside the img tag -->

<img src="photo.jpg" alt="smiling cat" < />

Remove the stray < character:

<!-- ✅ Fixed: no extra "<" -->

<img src="photo.jpg" alt="smiling cat" />

Missing > on a preceding tag

When a tag is missing its closing >, the parser continues reading the next tag as though it were part of the first tag's attributes:

<!-- ❌ The opening <div> is missing its closing ">" -->

<div class="wrapper"

<p>Hello, world!</p>

</div>

The parser sees <p> while still inside the <div> tag, triggering the error. Add the missing >:

<!-- ✅ Fixed: <div> is properly closed -->

<div class="wrapper">

<p>Hello, world!</p>

</div>

Missing > on a tag with multiple attributes

This often happens with tags that have many attributes, making it easy to miss the closing >:

<!-- ❌ The <a> tag is missing its closing ">" -->

<a href="/about" class="nav-link" id="about-link"

<span>About Us</span>

</a>

<!-- ✅ Fixed: closing ">" added to the <a> tag -->

<a href="/about" class="nav-link" id="about-link">

<span>About Us</span>

</a>

Accidental angle bracket in an attribute value

If an attribute value contains a < that isn't properly quoted, the parser may misinterpret it:

<!-- ❌ Unquoted or broken attribute value with "<" -->

<div title=5<10>

<p>Content</p>

</div>

Ensure attribute values containing special characters are properly quoted and use HTML entities where needed:

<!-- ✅ Fixed: value is quoted and uses an entity for "<" -->

<div title="5&lt;10">

<p>Content</p>

</div>

How to debug this error

When you see this error, follow these steps:

1. Go to the line number reported by the validator.
2. Look at the tag on that line — check if it has a stray < character.
3. If the tag looks fine, check the tag immediately before it — a missing > on the previous tag is often the real culprit.
4. Verify all attribute values are properly quoted — unquoted values containing < can trigger this error.
5. Use a code editor with syntax highlighting — mismatched or broken tags are usually easy to spot when the syntax colors look wrong.