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A couple weeks ago, Google has vastly improved their site move documentation, while also updating their mobile smartphone documentation.
Alistair Lattimore posted on Google+ asking why the documentation for smartphone guidelines specifically recommends using 302 redirects over 301 redirects? 301s have always been the recommended path for SEO purposes because they pass the best link equity from URL A to URL B.
But no, Google specifically wrote a 302 in the documentation on purpose:
I asked Maile Ohye and Matt Cutts of Google if this was indeed on purpose and Maile said it was 100% on purpose and not a mistake. Matt Cutts said the reason was because you may want to change it in the future and they didn't want it to be a permanent thing.
I should clarify, only use 302s when moving from the same URLs to separate URLs. Make sure you read the documentation carefully when going this route.
Forum discussion at Google+.
Comments:
victorpan
06/17/2014 01:22 pm
So if I have sites A, B, and C and their .m variants are going to be merged to site A when it gets redesigned... The mobile pages of site B and C should have 302's to site A's' mobile pages?
keaner
06/17/2014 04:08 pm
clear as mud once again google, jesus
Fedor
06/17/2014 08:55 pm
Ok, just to be clear. 301 Moved Permanently The requested resource has been assigned a new permanent URI and any future references to this resource SHOULD use one of the returned URIs. 302 Found The requested resource resides temporarily under a different URI. Since the redirection might be altered on occasion, the client SHOULD continue to use the Request-URI for future requests. This is taken directly from w3 rfc... Which one makes more sense to you? How often do you move things temporarily anyway?
David Watkinson
06/18/2014 08:11 am
From what I have read, you only need a 302 if you have a separate address for smartphone users and if that address is automatically loaded when the user-agent is detected. If you do not do this, then a 301 should be used. I believe the concern is that smartphone pages may change address, so a 302 should be used so that it is not permanent. Very few of us actually have a different address for smartphone users unless you are running something that specifically needs to be displayed significantly different from your normal visitors.