Bad value for attribute “href” on element “a”: Illegal character in query. “|” is not allowed.

The href attribute on an <a> element contains a literal pipe character (|), which is not a valid character in a URL according to RFC 3986.

URLs have a defined set of allowed characters. The pipe character (|) is not among them. While most browsers will silently encode the pipe and follow the link anyway, the HTML specification requires that href values contain valid URLs. Characters outside the allowed set must be percent-encoded before being placed in the markup.

The percent-encoded form of | is %7C. Replace every literal | in the URL with %7C to produce a valid href value.

HTML examples

Invalid

<a href="https://example.com/search?fields=name|date|status">Search</a>

Valid

<a href="https://example.com/search?fields=name%7Cdate%7Cstatus">Search</a>

Learn more:

MDN Reference

HTML a element - MDN

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MDN Reference

What is a URL? - MDN

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WHATWG Spec

URL Living Standard

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