We all know that making HTTP to HTTPS site migrations is unique, it is treated differently by Google. Google said when making such a migration, they strongly recommend you use a 301 redirect (not a 302 or 303) on a URL by URL basis. If you do not, then the migration will take a lot longer.
Google’s John Mueller said this at the 23:43 mark into the hangout yesterday. He said “We strongly recommend use clean 301 redirect from on a per URL basis for HTTP migrations.” If you do not, they might “have to reconsider and think well are they doing something unique here that’s not just a generic site move” and that can make “these moves take a lot longer and makes it a lot harder,” he added.
Here is the transcript:
Can we also use a 303 status code after moving from HTTP to HTTPS or as only 301 recommended?
We strongly recommend use clean 301 redirect from on a per URL basis for HTTP migrations.
So you can use other types of redirects but the 301 redirect is really the one that we watch out for. And if we can recognize that it’s really a clean migration from HTTP to HTTPS, that all of the old URLs have moved to the new one, that you’re not removing things, that you’re not noindexing or robots.txt disallowing pages differently on HTTPS. Then that makes a lot easier for us to trust that as a kind of this one big thing of a site move that is moving from HTTP to HTTPS.
So the clearer you can tell us that this is really just a generic move and we don’t have to think about any of the details, the more likely we can just switch that over without you seeing any big change at all.
So if you start using other kind of HTTPS result codes for redirects then that makes it such that we kind of have to reconsider and think well are they doing something unique here that’s not just a generic site move? And then at that point we have to reprocess really each URL individually and think like well what is the webmaster trying to do here in this specific case. And that makes these moves take a lot longer and makes it a lot harder for us to just pass on all of the signals to the new version of the site.
Google has recommended keeping these HTTPS migrations straight forward since day one. Moving the whole site at once, keeping the same structure and things will go well. At least now, if you mess up, Google may tell you about the issue.
Forum discussion at Google+.