Google Shares How 301 Redirects Pass PageRank


Google Shares How 301 Redirects Pass PageRank
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Google’s John Mueller offered an interesting explanation of how a 301 redirect will pass 100% of PageRank. The SEO community has known since about 2016 that there was no PageRank loss. But this is the first time that the “how” part of it has been discussed in this much detail.

Regardless of what John Mueller said, 100% PageRank does not pass through 301 redirects in all situations.

301 Redirects Cannot Always Pass 100% PageRank

The way PageRank works is that a little bit of it is lost with each link. PageRank was designed to pass less than 100% PageRank. This “decay” in PageRank was by design for a variety of reasons to do with modeling how authoritative a web page is.

301 redirects presented an interesting problem in how much PageRank to assign. Google ultimately decided to diminish the amount of PageRank that flowed from a redirect, just like any other link.

In 2013, Google’s Matt Cutts alluded to one of the reasons for this choice. Matt Cutts shared in a Google Webmasters video that if Google assigned 100% PageRank through 301 redirected links, then this would open the door to manipulating Google’s PageRank.

Screenshot of Google's Matt Cutts discussing PageRank and 301 redirects in a Webmaster Help videoMatt Cutts shared how much PageRank passes from a 301 redirect and why the amount of PageRank was subject to decay.

The way a publisher could exploit 301 redirects is by eliminating PageRank decay through 301 redirects. A publisher could link from their home page to all inner pages with 301 redirects and pass 100% of PageRank from link to link to link.

Matt Cutts issued the following guidance on how much PageRank passes 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 of PageRank and Redirects

Redirect chains have traditionally been problematic for search crawlers. I suspect that’s less of an issue today. But in the past the situation was so bad that a chained redirect (when a redirect is redirected to a URL that is redirected to another URL), could case a web page to display zero PageRank in Google’s toolbar.

Many years ago a very important company came to me to help them fix their zero PageRank problem. This company was a large and very important company. They were concerned about why they had zero PageRank showing on Google’s PageRank toolbar. It turned out that it was caused by excessive redirect chains. This turned out to be a bug at Google and it was subsequently fixed on their end.

How Does Google Assign PageRank through 301s?

That is the background to the 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 is a fascinating answer because Mueller introduces the concept of using the Canonical URL process for assigning PageRank. This means that there is no longer the issue of PageRank decay.

As for redirect chains, John Mueller went on to caution in their use:

“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 almost 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. All 301 redirects do not pass 100% PageRank.

A redirect from one page to an entirely different page will result in no PageRank being passed and will be considered a soft 404.

An SEO asked John Mueller in 2017 about this. There is a practice called Link Reclamation. Link Reclamation is the practice of reviewing 404 (page not found) response codes that are caused by a site linking to a page that does not exist.

In theory, redirecting that link to a page that does exist will cause the PageRank to flow to the redirected page. That’s link reclamation, reclaiming an otherwise wasted link and the associated PageRank.

The question posed to John Mueller was on the topic of Link Reclamation. Would redirecting links from 404 pages to existing pages not pass PageRank.

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 other words, the 301 redirect will pass 100% PageRank only if the redirect was a redirect to a new page that closely matched the topic of the old page.

Screenshot of John Mueller on Twitter answering why Google will or will not pass PageRank in 301 redirectsGoogle’s John Mueller explains how 301 Redirects will pass or not pass PageRank

This is interesting because it’s similar to how a canonical URL is handled. Canonical URLs are suggestions and Google does not accept the canonical suggestion if the canonicalized page is substantially different.

Cleverly, this also solves the problem of dealing with a rogue publisher who would link to all their web pages with redirects in order to conserve 100% of their PageRank.

Watch the Google Webmaster Hangout here.

Screenshots by Author, Modified by Author

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