When you’re studying up on SEO best practices, at some point you’ll probably come across the terms “301 redirect” and “302 redirect.” If the only HTTP status code you’re familiar with is the “404 Page Not Found,” then this might seem a bit confusing. Fortunately, 301 and 302 redirects are much better than a 404, and one of them can help you maintain your search rankings when making changes to your website — if you use it correctly.
301 Moved Permanently Redirect
A 301 redirect is simply a way of changing a web page’s address. In an ideal situation, all the content (such as text, images, layout and title tag) stays the same, and only the URL changes. 301s are useful when you move your site to a new domain.
What you need to know about the 301 redirect is that it passes about 85-90% (estimates vary) of the original page’s “ranking juice” to the new page. But that number might be a lot lower if the new page has little in common with the original page.
Why would you redirect to a new page that has little relevance to the content of the original page? Sometimes, when a site is completely redesigned, the webmaster creates 301 redirects to send all the old site’s pages to the homepage of the new site. Google discourages this practice and offers its own best practices for moving your website.
Google recommends moving your entire site to the new domain, and then making changes. Or if that’s not possible or feasible, Google’s advice is to redirect each individual page of the old site to a corresponding page on the new site — a painstaking process, but one that could potentially be better for your PageRank.
302 Found (HTTP 1.1) or Moved Temporarily (HTTP 1.0)
Unlike a 301 redirect, which is permanent and passes along a high percentage of ranking power, a 302 redirect is temporary and, it is thought, passes along 0% ranking juice.
When might you use a 302? Is it ever a good idea? SEO professionals generally discourage the use of 302s because they are often used incorrectly. But now there is evidence that the search engines, because they realize that people make mistakes, often treat 302s as “soft” 301s.
307 Moved Temporarily (HTTP 1.1. Only)
This code is the HTTP 1.1 version of the 302 redirect, and it is usually treated like a 302 by the search engines. However, if you need to do a temporary redirect and are not sure if the server is 1.1 compatible, it’s probably better to use a 302 than a 307.
Bottom line: Because 301 redirects are proven to pass along a significant amount of PageRank to the new page (as long as it is relevant), they are usually recommended more than 302s, which have always been thought to drop PageRank like a hot potato. The search engines might cut you some slack or they might not, which is why you should redirect with care.