Why a page is it not indexed by Google?

Some pages of my site do not appear in results of search engines. What could be causing this?

To determine whether a page is indexed or not, use in the query bar of the search engine, the command:

site: sitename.extension

It may be present but in the depths of the ranking, or completely absent. This may have several causes...

  1. Maybe the HTML code is it not correct and therefore not recognized by robots parsers...
    Check the syntax with the W3C validator.
  2. If the page is new, it takes several days or weeks for it to be taken into account.
  3. The page is not known by search engines because no link allow them to access it. You must verify that it is accessible from another page.
  4. Indexing is prohibited by a meta-tag inside the page.
    <meta name="robots" content="none">
    <meta name="robots" content="noindex">
  5. The canonical tag indicates that this page is located at another address.
  6. The robots.txt file prohibits crawlers from accessing the page. Therefore it can not be indexed.
    It may take the form: 
    User-Agent: *   
Disallow: /dir/filename.html
  7. It is also possible that Google or another search engine decides not to index your website because the robots.txt file is malformed. See what is a robots.txt file.

How to make a page be indexed

The only way is to have a link to this page from another page already indexed. This may be an internal link or from another site.
It may also be a link in a sitemap.

If a site is not indexed as a whole, the first thing to check is the robots.txt file to see if it does not block robots. Robots are blocked with a directive of the form Disallow: /
They are not blocked if nothing follows Disallow.

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