Bad value X for attribute “href” on element “a”: Illegal character in path segment. “^” is not allowed.

The href value on the <a> element has a literal ^ (caret) in its path, and a URL can only carry that character percent-encoded as %5E.

The URL standard doesn't list ^ among the characters a URL can contain. Browsers still follow the link, but the markup is invalid.

The caret usually comes from a file name. A document saved as meeting-minutes-^2.pdf and uploaded to a CMS keeps the caret in its address, and every link to it repeats it. Rename the file without the caret and update the links, adding a redirect from the old address if other sites link to it. If the file has to keep its name, write the caret as %5E in the href. The server decodes %5E back to ^ when it looks up the file, so the encoded link still opens the same document.

A caret in the query string or the fragment gets a different message, ending in "Illegal character in query" or "Illegal character in fragment". When the href is very long, the validator leaves the value out of the message. The cause and the fix are the same.

Invalid example

<a href="/files/meeting-minutes-^2.pdf">Meeting minutes (PDF)</a>

Valid example

Rename the file so its name has no caret:

<a href="/files/meeting-minutes-2.pdf">Meeting minutes (PDF)</a>

If the file name can't change, percent-encode the caret:

<a href="/files/meeting-minutes-%5E2.pdf">Meeting minutes (PDF)</a>

Learn more:

MDN Reference

MDN Web Docs: The Anchor element

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MDN Reference

MDN Web Docs: Percent-encoding

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WHATWG Spec

WHATWG URL Living Standard

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