Google’s John Mueller provided an intriguing explanation about how a 301 redirect can pass 100% of PageRank. Since around 2013, the SEO community has understood that there is essentially no PageRank loss beyond the normal link-to-link decay. However, this is the first time the "how" part of it has been explained in such detail.
Despite John Mueller’s explanation, not all 301 redirects carry 100% PageRank in every situation.
301 Redirects Cannot Always Pass 100% PageRank
PageRank inherently loses a small fraction with each link. It was intended to pass less than 100% PageRank, as this "decay" was part of the original design to accurately model the authority of a web page.
The question of how much PageRank to transfer through 301 redirects posed a unique challenge. Google eventually chose to reduce the amount of PageRank conveyed through a redirect, similar to other links.
In 2013, Matt Cutts from Google highlighted one of the reasons for this decision. In a Google Webmasters video, he mentioned that allowing 100% PageRank to flow through 301 redirects could lead to manipulation of Google’s PageRank.
The potential for abuse comes from eliminating PageRank decay using 301 redirects. A publisher could link from their homepage to internal pages using 301 redirects and transmit 100% PageRank through each link.
Matt Cutts offered this guidance about the PageRank passed through 301 redirects at a search conference:
“I mentioned that a certain amount of PageRank also dissipates through 301s. …The amount of PageRank that dissipates through a 301 is almost exactly, is currently identical to the amount of PageRank that dissipates through a link.”
My Personal Experience with PageRank and Redirects
Redirect chains have historically been troublesome for search crawlers. While this is likely less of an issue today, it was once so problematic that a chained redirect (where a redirected URL leads to another redirected URL) could show a web page with zero PageRank in Google’s toolbar.
Years ago, an important company enlisted my help to solve their zero PageRank issue. This large, influential company was concerned about displaying zero PageRank on Google’s toolbar, which was ultimately caused by excessive redirect chains. It turned out to be a bug in Google’s system that was later resolved.
How Does Google Assign PageRank through 301s?
This is the background to a question asked of John Mueller in a recent Webmaster Hangout.
The question posed in Google’s Webmaster Hangout:
“Is there any link equity loss from redirect chains?”
Google’s John Mueller answered:
“For the most part that is not a problem. We can forward PageRank through 301 and 302 redirects. Essentially what happens there is we use these redirects to pick a canonical. By picking a canonical we’re concentrating all the signals that go to those URLs to the canonical URL.”
This response is fascinating because Mueller introduces the idea of using the Canonical URL process for PageRank assignment, which suggests the issue of PageRank decay is no longer a concern.
Regarding redirect chains, John Mueller advised caution:
“So for example, when it comes to links, we will say well, it’s this link between this canonical URL and that canonical URL- and that’s how we treat that individual URL.
In that sense, it’s not a matter of link equity loss across redirect chains, but more a matter of usability and crawlability. Like, how can you make it so that Google can find the final destination as quickly as possible? How can you make it so that users don’t have to jump through all of these different redirect chains? Because, especially on mobile, chain redirects, they cause things to be really slow.
If we have to do a DNS lookup between individual redirects, kind of moving between hosts, then on mobile that really slows things down. So that’s kind of what I would focus on there.
Not so much like is there any PageRank being dropped here. But really, how can I make it so that it’s really clear to Google and to users which URLs that I want to have indexed. And by doing that you’re automatically reducing the number of chain redirects.”
Do All 301 Redirects Pass 100% PageRank?
No, not all 301 redirects pass 100% PageRank.
A redirect from one page to an entirely different page won’t transfer PageRank and will be treated as a soft 404.
An SEO asked John Mueller in 2017 about link reclamation. This practice involves reviewing 404 response codes caused by links to non-existent pages and redirecting them to existing pages to allow PageRank to flow to the redirected page.
The question posed to John Mueller was about whether redirecting links from 404 pages to existing pages would allow PageRank to pass.
John Mueller responded:
“301-redirecting for 404s makes sense if you have 1:1 replacement URLs, otherwise we’ll probably see it as soft-404s and treat like a 404.”
In essence, a 301 redirect will only pass 100% PageRank if the redirect leads to a new page that closely matches the topic of the old page.
This strategy is reminiscent of how a canonical URL is handled. Canonicals are suggestions, and Google may not accept the canonical if the page content differs significantly.
Smartly, this approach also addresses the issue of publishers linking to all their web pages with redirects to preserve 100% PageRank.
Screenshots by Author, Modified by Author.
