Error in Google Webamaster “Referenced AMP URL is self-canonical AMP”
Means you have mentions canonical for AMP page is AMP URL of same page. Solution if you have to mention canonical for your AMP page is normal page or desktop version of your page.
For example: www.example.com/article-page.html
AMP version of above pages is: www.example.com/amp/article-page.html
For AMP version pages set canonical tag as<link rel=”canonical” href=”www.example.com/article-page.html” /> not <link rel=”canonical” href=”www.example.com/amp/article-page.html” />.
What “Referenced AMP URL is self-canonical AMP”
When you have both a non-AMP and an AMP version of the same page. Know how to make it that google can search, crawl and index that page.
If Google Search finds the non-AMP version of web page, then how does it know there’s an AMP version of it?
Life you have a web page:
Use This tag <link rel=”amphtml” href=”https://www.example.com/article-page.html”> to help google to identify normal page.
And use on AMP version to tell search engine about the desktop version of AMP page is
<link rel=”canonical” href=”https://www.example.com/article-page.html”>
What if I only have only APM page?
When you have decivedonle single version page pages, and that pages is AMP page. Then, you must still add the canonical link to it, which will then simply canonical to itself.
Example: <link rel=”canonical” href=”https://www.example.com/article-page.html”>
Is your AMP version or AMP web page valid?
Use this tool to check https://search.google.com/test/amp