Bad value X for attribute “target” on element “a”: Reserved keyword X used.

The target attribute specifies where to display the linked resource. The HTML specification defines a set of reserved keywords that all begin with an underscore: _blank, _self, _parent, and _top. Any other value starting with an underscore is considered invalid because the underscore prefix is reserved for current and future keywords defined by the specification.

This matters for several reasons. First, browsers may handle unrecognized underscore-prefixed values inconsistently — some might treat them like _blank, while others might ignore them entirely or treat them as named browsing contexts. This leads to unpredictable behavior across different browsers. Second, using reserved but undefined keywords signals a likely typo or misunderstanding of the attribute, which could cause navigation to behave differently than intended. Standards compliance ensures your links work reliably for all users.

The valid keywords and their meanings are:

• _self — Opens the link in the current browsing context (the default behavior).
• _blank — Opens the link in a new, unnamed browsing context (typically a new tab).
• _parent — Opens the link in the parent browsing context, or _self if there is no parent.
• _top — Opens the link in the topmost browsing context, or _self if there is no ancestor.

If you need to target a specific named frame or window, simply use a name without a leading underscore. Any string that doesn’t start with _ is treated as a valid named browsing context.

Examples

Incorrect: Invalid reserved keyword

These examples use underscore-prefixed values that are not recognized keywords:

<!-- Typo: "_blanks" is not a valid keyword -->

<a href="https://example.com" target="_blanks">Example</a>

<!-- "_new" is not a valid keyword -->

<a href="https://example.com" target="_new">Open in new tab</a>

<!-- "_tab" is not a valid keyword -->

<a href="https://example.com" target="_tab">Open link</a>

Correct: Using a valid keyword

<!-- Use "_blank" to open in a new tab -->

<a href="https://example.com" target="_blank">Example</a>

<!-- Use "_self" to open in the same tab (also the default) -->

<a href="https://example.com" target="_self">Example</a>

<!-- Use "_parent" to open in the parent frame -->

<a href="https://example.com" target="_parent">Example</a>

<!-- Use "_top" to open in the topmost frame -->

<a href="https://example.com" target="_top">Example</a>

Correct: Using a custom named browsing context

If you intend to target a specific named window or frame rather than using a keyword, remove the underscore prefix:

<!-- Valid: "myframe" is a custom browsing context name -->

<a href="https://example.com" target="myframe">Open in myframe</a>

<!-- Valid: targeting a named iframe -->

<iframe name="content-frame" src="about:blank"></iframe>
<a href="https://example.com" target="content-frame">Load in iframe</a>

A common mistake is using _new with the intention of opening a link in a new tab. While some browsers may treat _new similarly to _blank, it is not a valid keyword. Use _blank instead. Note that when using target="_blank", it’s a good security practice to also include rel="noopener" (though modern browsers now do this by default):

<a href="https://example.com" target="_blank" rel="noopener">Example</a>

Learn more:

WHATWG Spec

HTML Spec: links created by a elements

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WHATWG Spec

HTML Spec: valid browsing content or keyword

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