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:

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+.