For seems like forever, webmasters and seo professionals were hesitant to use redirects except in the most extreme cases. There was no real choice when it came to redirection so you did it knowing that there were going to be issues that could not be fixed quickly. Things have changed now but for the sake of illustrating the changes here are how redirects were handled until recently:
301 redirects lose about 15% of pagerank. This was confirmed back in 2013 by Matt Cutts when he explained that Google treated a 301 redirect the same way it treated a link.
302 redirects do not pass any pagerank at all. 302’s are supposed to be temporary redirects and as a result were not expected to last long.
HTTPS migrations result in a lot of pagerank losses due to the massive number of 301 redirects required. The bigger the site, the more pagerank was lost due to the compounding nature of internal links.
Now, Google has revealed the following changes:
Back in February in a Q&A about migrating a site to HTTPS, Google’s John Mueller announced that no PageRank is lost for 301 or 302 redirects:
“Do I lose “link juice” from the redirects? No, for 301 or 302 redirects from HTTP to HTTPS no PageRank is lost.”
This is largely seen as a move to encourage hesitant webmasters to move their sites to HTTPS.
Then Google’s Gary Illyes told the SEO world that Google doesn’t care which redirection method you use, be it 301, 302, or 307. Basically Google will figure it out and they all pass PageRank.
He went further recently and tweeted that 3xx (meaning all 300 redirects) no longer lose PageRank at all.
This move should greatly speed up the adoption of HTTPS now.