What triggers this issue?
This report lists pages that reference more than one URL for the same language (or language-location) in their hreflang annotations.
Example in page header:
<head>
...
<link rel="alternate" hreflang="en" href="https://ahrefs.com/blog/google-keyword-planner/" />
<link rel="alternate" hreflang="en" href="https://ahrefs.com/blog/es/planificador-palabras-clave-google/" />
...
</head>
Example in HTTP header:
Link: <https://ahrefs.com/blog/google-keyword-planner/>; rel="alternate"; hreflang="en",
<https://ahrefs.com/blog/es/planificador-palabras-clave-google/>; rel="alternate"; hreflang="en"
Why is it important?
Announcing multiple pages for the same language (or language-location) in hreflang annotations can confuse search engines. Such hreflang annotations can be misinterpreted or ignored by the search engines.
How to fix it?
Review all the pages listed in this report. Make necessary edits to their hreflang annotations on these pages so that only one page is referenced for one language.
Note that you're free to announce multiple pages for the same language if you're using the "language-location" code in your annotations.
E.g.
<link rel="alternate" hreflang="en-gb" href="href="https://ahrefs.com/blog/en/google-keyword-planner/" />
<link rel="alternate" hreflang="en-us" href="href="https://ahrefs.com/blog/google-keyword-planner/" />
These annotations will be valid.