Read the below points to understand about Google search console (webmasters) coverage report and index your website more efficiently.
Discovered – Currently Not Indexed:
Google finds the URL via backlinks, internal linking, sitemap, etc. and add it to the queue for indexing but not indexed yet, because of limited crawl budget issue.
Crawled – Currently Not Indexed:
In this Google crawl the URLs but didn’t index it, because Google thinks that the content on the page is less-worthy for users thus it doesn’t include the URLs for indexing. The most common issues are low-quality content, spammy content, doorway pages, and outdated content.
Duplicate Without User-Selected Canonical:
Google considers that these pages have duplicate content and there is no clear canonical tag on those pages. Google thinks that these pages are not to be canonical and suggested these pages to be excluded from the index.
Duplicate, Submitted URL Not Selected as Canonical:
Same as “Duplicate without user-selected canonical”. The only difference is that you ask Google to index these pages by adding URLs on the XML sitemap.
Duplicate, Google Choose Different Canonical Than User:
On these pages, a user mentioned canonical tag but Google disagrees with the URL mentioned in the canonical tag and chooses different URLs to index as the canonical, other than the mentioned URL in the canonical tag.
Submitted URL Not Found (404):
The URLs you submitted, via the sitemap.xml file, doesn’t exist.
The main cause of this error is – redirect loop, excessively long URL, and redirect chains 5 or more URLs long.
Server Error (5xx):
Internal server error, in this server, returns a 500 status code.
Because of some undefined reason your URL is prevented from being crawled. Even Google doesn’t know what it is exactly. You can fetch the URL/page using the URL Inspection tool (Search Console) to check any 4xx, 5xx or any other error. In case you don’t find any clues than send the URL to your development team.
Indexed, Though Blocked by Robots.txt:
If a URL is blocked by the Robots.txt file but that particular URL has other strong ranking signals, such as links, Google my deem the robots.txt rule and index the URL.
To block a page definitively from appearing in Google SERPs, don’t use robots.txt. You need to use the Noindex tag or prohibit anonymous access to the page. URLs with a Noindex tag will be crawled less frequently and if present for a long time, it will eventually lead Google to Nofollow the page’s links as well, which means they won’t add those links to the crawl queue and other ranking signals won’t be passed to linked pages.
Indexed, Not Submitted in Sitemap:
In this, the URLs were fetched by Googlebot through a link and then index. But that particular URL is not submitted in the sitemap.xml file.
Submitted URL Blocked by Robots.txt:
In this, a URL is submitted via XML sitemap and also blocked by the robots.txt file. You need to either remove the URL from the XML sitemap or remove the robots.txt rule with block the URL for being indexing.
Submitted URL Marked “Noindex”:
The URL you submitted, likely via the sitemap.xml is marked as noindex either via robots meta tag or via HTTP header X-robots tag.
Submitted URL Returns Unauthorized Request (401):
In this Googlebot is not authorized to crawl the URL you submitted. In this, the crawling is prohibited on password-protected pages.