Google's John Mueller has said many times that 302s vs 301s are pretty much the same thing in terms of how Google treats redirects. He often said not to worry about using a 302 over a 301 or the other way around. The question is why? John basically said that most of the web uses both the same so Google uses multiple signals to determine how permanent a 302 redirect is or is not.
If Google sees a 302 redirect in place for several months, one would assume Google would change the status of the "temporary" redirect meaning of a 302 status code and treat it more like a 301 redirect, which is a "permanent" redirect.
What does this technically mean to Google? John Mueller explained on Twitter and as we explained here before, "with redirects, we tend to put URLs into the same bucket, and then use canonicalization to pick which one to show," John said. "The rankings will generally be the same, so whether it's source or destination URL doesn't really matter," he added. "
"A temporary redirect (like a 302) is more about telling us the source URL might be preferred, while a permanent one suggests the destination URL would be. We use a lot more than just redirects for canonicalization though. That's usually why a 302 "source-preferred" ends up being treated more like a 301 "destination-preferred" over time. For example, if all internal & external links point to the destination, probably we should pick the destination too. There's no fixed cut-off time for that."
Over time, Google has to just figure it out. Most developers don't think twice about how Google sees a 301 vs a 302 redirect, that is just fact. So Google knows that and deals with it.
Here are those tweets:
With redirects, we tend to put URLs into the same bucket, and then use canonicalization to pick which one to show. The rankings will generally be the same, so whether it's source or destination URL doesn't really matter.
— 🍌 John 🍌 (@JohnMu) April 8, 2021
That's usually why a 302 "source-preferred" ends up being treated more like a 301 "destination-preferred" over time. For example, if all internal & external links point to the destination, probably we should pick the destination too. There's no fixed cut-off time for that.
— 🍌 John 🍌 (@JohnMu) April 8, 2021
Forum discussion at Twitter.