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Do 301 Redirects Result in PageRank Decay?

by Bruce Clay April 15, 2010

Technology changes. Web sites evolve. Page content becomes obsolete. Outdated content is replaced with current content. A site must always evolve and improve, or die.

Whenever progress is made, when new pages replace old ones, there's only one good solution to handle the passing of link value from the old to the new. When tasked with replacing pages while also retaining rankings, the best option is still the tried and true 301 redirect.

The Effect of 301 PageRank Decay

The 301 permanent redirect has always been the preferred option of redirecting users and search engines from old pages to new. However, some doubt has been cast on the use of 301 redirects ever since Matt Cutts, the head of Google's Web spam team, said that a decay of PageRank occurs when a 301 redirect is implemented.

Our testing indicates that PageRank certainly transfers through a 301 redirect, so any decay that occurs must be a very small fraction that is barely detectable. What tiny amount of PageRank that is lost is likely less than the evaporation that occurs through a nofollow link attribute, and it is much less than the PageRank loss sustained if the old page is not redirected at all.

No matter how you look at it, 301 redirect PageRank decay is less than the potential revenue loss of a user hitting a 404 error, and it is far smarter to 301 redirect a page than to split PageRank between several domains and pages when not using a redirect. By any measure, a 301 redirect is still the ideal way to replace an old URL with a new one.

An SEO's Redirect Options

An SEO has several alternatives when moving a page:

  1. A new page with no PageRank redirection from the old page: The new page will not receive link credit from the old page, thus it will not be seen by the search engines as important. Traffic will suffer and ranking opportunities will be missed.
  2. A new page with the old page 302 redirected: The new page will be seen as a duplicate of the old page, with the old page using the new content. PageRank is not transferred to the new page.
  3. A new page with a Meta refresh or JavaScript redirect from the old page: The new page won't necessarily receive a transfer of PageRank, and a red flag is raised by search engines suspicious of signs of cloaking/spamming.
  4. A new page with the link "canonical" tag: The new page will likely be seen by search engines as the authority page, and will be the target for search indexing and PageRank. However, it is a newly introduced solution and there are issues with it that are still being worked out. It's also unclear if all search engines support this tag in the same way.
  5. A new page with the old page 301 redirected: The new page will receive the link credit from the old page, will often have search engine rankings far faster, and will give old-page users an improved experience. There is often a diminished bounce rate, and thus a higher conversion rate, as well as other long-tail benefits that come with a proper SEO project.

The choice for SEO is clear — go with option 5!

The Usability Factor

The issue of redirected pages goes beyond PageRank value and actually affects a user's experience with a site. Suppose you clean up a URL, improve page load performance, and perform SEO on the content of a page. The end result is a new page with an improved user experience.

With this new page in tow, there are several usability reasons why you'd want to remove the old page and replace it with the new. First, you want to avoid confusing your users with two similar pages, so you want to remove the old page from the site. You also want the new page to rank because it provides a better user experience and has the ability to perform better in search results, thanks to SEO improvements. But in order to give your new page the best opportunity to rank, you need to transfer the PageRank of the old page. A permanent 301 redirect solves both problems.

Practical Problems of Implementation

Have you ever changed technologies on your site? Do you know someone that upgraded to .net (ASPX), or upgraded to WordPress, or redesigned their site, or purchased a competitor, or any number of other events that occur naturally on the Web? There are many reasons why an SEO or webmaster might need to implement a redirect. Yet while the 301 redirect is always the preferred solution, it might not always be at his or her disposal.

Review previous articles in our newsletter to understand the requirements of implementing a 301 redirect. In Sorting Out Redirects, you'll find a guide for doing a 301 redirect using .htaccess for an Apache server, as well as instructions for performing a redirect on a Microsoft IIS 5.0 or 6.0 server. In Methods and Implementation of Redirects, you can view the steps for implementing a 301 redirect on a Microsoft IIS 7.0 server.

If a site is written in a dynamic language like PHP or ASP, there are also ways of implementing a 301 redirect using code that is uploaded to a site through FTP access. However, a server-side redirect is the cleanest method of implementation, and access to your site's server is a basic need when creating a server-side 301 redirect. If your site's current host doesn't allow server access, it may be time to find another host.

301 Redirects: Still the Best Choice

Whenever a new technology comes along to replace the old, there is no better option than implementing the 301 permanent redirect. You would never replicate your site and let both rank, and doing a 301 in that situation is natural and proper.

Don't hesitate because you fear PageRank decay, which is minimal at most. Implement a proper 301 redirect and let your PageRank flow. Be happy with the boost in rankings and traffic that occur with your improved site or pages. And don't hold on to the notion that the old URLs will somehow help you down the line. It's your new pages and site that require your investment. You made these vital moves for a reason.

The 301 redirect is standard fare for SEOs everywhere, and that's because it's our friend. It's a powerful tool for helping users and search engines find replaced pages. And it's the only redirect option that keeps intact the link value so important to search engine rankings.

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