Google Assumes Domains Are the Same If Duplicate Parameters Used on Shared Hosting
If you have shared hosting for different websites and specify the same URL parameters for each one then Google may assume that the domains are the same or equivalent.
Parameters Applied at Site Level Recommended as They Are Easier to Manage
John recommends applying parameters in Search Console at a site level as this is easier to manage than at a page level. However, if the same parameter changes the content on one page but is irrelevant on another then you will need to separate these in Search Console.
Parameters Are Hint to Google Not to Crawl as Frequently
Parameters in Search Console aren’t a directive, more of a hint to Google not to crawl these as frequently. Blocking URLs in Robots.txt is strong directive to say Google should not be looking at these pages e.g. if Google’s crawls are crashing your site.
Avoid Internal Tracking Parameters or Make Google Aware in GSC
Internal links with parameters does affect crawling and indexing, as Googlebot could potentially be crawling a lot of URLs that lead to the same content and aren’t as useful for search. The parameter handling tool is GSC can be used in these cases to let Google know these parameters can be ignored or you can avoid using internal tracking parameters.
Google Spot Checks Parameters Applied in GSC
Google tries to apply parameters set in the URL Parameters section of Search Console, like "Doesn’t affect page content". Google also spot checks these URLs, stripping away the parameter and crawling the simplified URL to check that this setting is correct.
Add Self-Referential Canonical Tags
Add self-referential rel canonicals to pages as it gives Google a clear indication of what page is to be indexed. Even if there is just one page, there may be different variations such as parameters – a rel canonical will clean these up.
URL Parameters Make it Easier for Search Engines to Crawl your Site
URL Parameters make it easier for Google to understand the URL structure, and identify which URLs to ignore. Having parameters in the url path can make it harder for Google to understand.
Session IDs should be a Separate Parameter
If you add session IDs as a separate parameter instead of a semi-colon, then they can be managed more easily with the Search Console Parameter handling tool
URL Parameters Help Crawling and Indexing
URL parameters in URLs make it easier for Google to understand URLs for crawling and indexing. If you put everything into the path of the URL it can be harder for Google to crawl them properly.