We have some legacy 302 redirects in place on our site that should have always been 301s. We've now changed the redirects to 301s but various SEO tools (and presumably Google) still see the 302 redirect rather than the 301.
My question is, how long do 302s normally get cached for (if there is a 'normally' in this situation)? And is there anything we can do to speed up the process of recognising the change to 301s?
302 Caching
A 302 response code would only be cached if accompanied with the Cache-Control or Expires headers. There is no explicit or embedded cache information within a 302 response.
According to RFC 2616, section 10.3.3 302 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 response is only cacheable if indicated by a Cache-Control or Expires header field.
Verify 301 Response
I recommend you verify that you are indeed sending the expected 301 HTTP responses. You can use:
curl -I http://www.domain.com/
to see the headers being returned.
Alternatively, you can use http://redbot.org to explore HTTP headers as well.
If you are certain you are sending the correct headers, then Google will see these on its next visit.
Check Logs
You can then check your logs to see if Googlebot has visited the pages with the updated headers. If it has, then it should pick up the 301 response.
Once this is done, the change should be included in the next search engine update.
