If you want to confuse Google use a 302 redirect
You would usually take it for granted that the final step of any relaunch or domain move would be the permanent redirection of the old URLs to their new counterparts, with the help of 301-redirects. This permanent redirect lets google know that the entire website has moved and that, in the future, only the new website should show up in the search results. Which makes a lot of sense! So much for theory.
Out in the wild, we get to see cases, from time to time, where a temporary 302-redirect is used for a permanent move. This redirect is supposed to be a notice that a document is temporarily somewhere else.
The age-old question is whether there really is a difference when it comes to a 301- or 302-redirect?
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What does a 302-redirect do?
The server response 302 signals a browser that the requested resource is available, but temporarily at a different location – Found (Moved Temporarily). The user is sent to the new location. This kind of redirect makes sense if your content might be available at a different URL for a specific timeframe, for example during a server move.
How does Google react?
Google sees a 302-redirect as one thing above all: the old URL should still be shown in the search results. Google makes the correct assumption that this redirect will only stay around for a while. This means that webmasters who use 302-redirects as a permanent fixture may not see all the trust signals, that their original documents managed to collect, get passed on to the new URL. If, for example, you were to use a 302-redirect to get rid of possible duplicate content issues, then a temporary redirect is the wrong choice.
The question that is still not fully answered to this day is, does Google really treat 302-redirects that are available for a long time as though they are permanent? Google states that, as far as trust signals are concerned, it should not matter which redirect is used. But is that reall the case?
John Mueller wrote the following on this topic:
When it comes to the correct use case of a 302-redirect, he answered most vaguely:
„302 temporary redirect: Like the name says, this might not be that permanent.”
Might not be that permanent
After the German domain ueberall.tv moved to tv-plattform.de, in 2015, we see a regular back and forth between both domains within the Visibility on Google. Looking through the archive.org results for the first domain, we see a meta-refresh in place between May 2015 and June 2016, which is then replaced by a constant 302-redirect, ever since.
Even though this 302-redirect does not seem to change, Google decides to show the old result within their search results for a significant amount of the time. Which makes this a nice example of how such a constellation can turn into an unfavourable interplay between the webmaster and Google.
Why do SEOs use 302-redirects?
If we are honest, there are only a few use-cases where a 302-redirect is useful. A move is not one of them, as these are usually permanent – just like in the real world. According to Google, they will always pass the PageRank values through any kind of 3xx-redirect. The real question here is why some (few) IT-managers are still so afraid of 301-redirects? Could it be that the old content will stop showing up in Google’s index? Is it the extra time and effort of setting the server configuration to use 301-redirects?
Whatever it may be: It becomes apparent how important the correct redirect can be, if we listen to John Mueller, one last time:
„The web isn’t perfect, search engines have to deal with what they find.”
And what search engines find, is up to us.