Notes from the Google Webmaster Hangout on the 3rd of September 2019.
Likely That Content Won't Be Indexed if Not Showing Up in Google Testing Tools
If Google's testing tools are able to fetch all of the different resources for a page, but there is content missing in the rendered output, it is likely that this content won't be able to be indexed.
Different Sections of a Site Can Rank Quicker Depending on Internal Linking Structure
Some sections of a site are structured more optimally for URL discovery and can be indexed and ranked more quickly. For example, the blog section on a WordPress site that has good internal linking and an RSS feed all set up might perform better than other parts of the site.
Google Can Crawl Different Parts of a Website at Different Speeds
Google is able to detect how frequently the different sections of a site are updated and crawl them at different speeds, so that the frequently changing pages are crawled more regularly.
Implement Redirects From Mobile Pages to Desktop Pages For Desktop Users
If you have a separate m-dot site, Google will usually pick this as the preferred canonical version after mobile-first indexing and the m-dot site will be shown in desktop search results. To avoid negative UX, implement redirects to the desktop version for desktop users.
Google Can Periodically Try to Recrawl 5xx Error Pages
If a server error is shown on a page for as long as a week, Google can treat this in a similar way to a 404 error and will reduce the crawling of that page and remove it from the index, but will still access the page every now and again to see if the content is available again. If so, the page will be indexed again.
Signals Are Kept For 4xx or 5xx Error Pages Previously Dropped from the Index When They Are Re-added
If your pages displayed a 4xx or 5xx error for a while and were dropped from the index but become available again after a month or so, for example, Google will be able to return them to the search results in the same state they were before. They won't have to start trying to rank from nothing.
Incorrectly Using the Vary User Agent HTTP Header Won't Stop Site Being Moved to Mobile-first
Using the Vary: User-agent HTTP header incorrectly isn't ideal, but Googlebot will still be able to find content on the page to index and won't be impacted much.
Mobile-first Indexing Isn't a Ranking Factor or Quality Signal
There's no need to push a site to be moved to mobile-first indexing. This is only a technical change in the way pages are crawled and indexed, and being in the mobile-first index doesn't come with any quality signals or ranking boosts.
Use Redirects & Canonical Tags to Stop Data From Other Site on Same IP Being Included in GSC
If there are internal links between two sites on the same IP address, data for both sites can sometimes appear in the same GSC account. If you don't want Google crawling the other site then add redirects or canonical tags pointing to the main site.
A Readiness Classifier & Algorithm is Used to Determine Mobile-first Indexing
A readiness classifier is used to determine whether or not pages are ready for mobile-first indexing and looks at elements like internal linking, anchor text and content differences. However, if the algorithm determines that the majority of pages are ready then the site will be moved, even if some pages have content inconsistencies. This could impact rankings.
Hreflang Can be Implemented on Small Groups of Pages
If you're only seeing issues with how your homepage is being displayed, then you can add hreflang to that page. You don't have to implement hreflang across large sections of the site.
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