Use 301 redirects while migrating from HTTP to HTTPS
Google says to use 301 redirects and not to get fancy with your HTTPS site migration by keeping it consistent and simple.
Google trends analyst John Mueller said not to use other types of redirects other than 301 redirects for these migrations. Because if we use any other redirects Google’s path leads down for reprocessing all the URL’s, which results in long time and harder work to pass all the signals to new version of the site. He also recommended to use 301 redirects on per URL basis while migrating from HTTP to HTTPS.
Google made a video on this the transcript of the video is below
Is 303 status code recommended after moving from HTTP to HTTPS or only 301 is recommended?
Clean 301 redirect is our strong recommendation to useper URL basis for HTTP migrations.
Other types of redirects also can be used but the 301 redirect is really the one that Google watch out for. If Google can recognize the migration from HTTP to HTTPS cleanly then that means all of the old URLs have moved to the new one. Which makes a lot easier for Google to trust that a site is moving from HTTP to HTTPS. This makes Google’s work clear and not to think about any details and switch the URL’s.
Any other redirect code other than 301 redirect is used then Google thinks that as a unique site move but not a generic one. Which makes Google to reprocess URL’s one by one and that makes a very long time and harder work for Google.
By this we can clearly know that 301 redirect is the recommended site code for the site migration from HTTP to HTTPS.