Crawling
Before a page can be indexed (and therefore appear within search results), it must first be crawled by search engine crawlers like Googlebot. There are many things to consider in order to get pages crawled and ensure they are adhering to the correct guidelines. These are covered within our SEO Office Hours notes, as well as further research and recommendations.
For more SEO knowledge on crawling and to optimize your site’s crawlability, check out Lumar’s additional resources:
404 or 410 Status Codes Will Not Impact a Website’s Rankings
If Google identifies 404 or 410 pages on a site, it will continue to crawl these pages in case anything changes, but will begin to phase out the crawling frequency to concentrate more on the pages which return 200 status codes.
Last Modification Dates Important For Recrawling Changed Pages on Large Sites
Including last modification dates on large sites can be important for Google because it helps prioritize the crawling of a changed page which might otherwise take much longer to be recrawled.
Google Has a Separate User Agent For Crawling Sitemaps & For GSC Verification
Google has a separate user agent that fetches the sitemap file, as well as one to crawl for GSC verification. John recommends making sure you are not blocking these.
Blocking Googlebot’s IP is The Best Way to Prevent Google From Crawling Your Site While Allowing Other Tools to Access It
If you want to block Googlebot from crawling a staging site, but want to allow other crawling tools access, John recommends whitelisting the IPs of the users and tools you need to view the site but disallowing Googlebot. This is because Google may crawl pages they find on a site, even if they have a noindex tag, or index pages without crawling them, even if they are blocked in robots.txt.
Ensure Google is Able to Crawl All Pages Involved Within Infinite Scroll
When implementing infinite scroll, ensure Google is able to reach all of the pages involved. John recommends the best way to do this is by linking to all the pages individually through a pagination set up, to ensure each page can be crawled.
Google is Unable to Crawl User-triggered Events
Googlebot cannot crawl user-triggered events, for example content loading once a user scrolls. John recommends using dynamic rendering to enable crawling of these events and ensuring the content loads with a link rather than an interaction.
Prevent Search Engines From Crawling Low Quality UGC
When working with user-generated content, John recommends filtering out high quality pages to ensure search engines are able to see this rather than the lower quality content.
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.
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.
Google Determines if Pages Need to be Rendered by Comparing Content Found in Initial HTML & Rendered DOM
Google compares the content of the raw HTML of a page from the initial crawl to the rendered DOM after rendering to see if there is new content and to determine if it needs to be rendered going forward.