At Wayfair.com, we conduct a lot of SEO tests. We’re continually measuring and assessing our strategies, some of which were shared in our last post for YouMoz, Accidental SEO Tests: When On-Page Optimization Ceases to Matter. Sometimes, however, we stumble across what we call “accidental SEO tests.” This ordinary happens when a bad code apply unintentionally hurts our SEO, and we end up learning something helpful from our mistake.

Tens of thousands of 301 redirects

One of our accidental tests included regularly 301-redirecting large batches (i.e., many thousands) of product pages. On average, we found a consistent (and basically permanent) traffic loss of about 15% for 301-redirected URLs.

Previously, Google has said a little amount of Page-rank is lost through a 301 redirect, which is the same as through a link. Presently, for the first time, we can put a hard number to how much that loss is.

Structure of an accidental SEO test

Like any great SEO team, our product pages were set to utilize the name of the product in the URL. Moreover, if for any reason a product URL was changed, the old URL was set to automatically redirect to the new one.

What we didn’t understand, though, is that our promoting teams were also busy being great at their jobs, part of which included changing the naming standards of products on a regular basis. Each change they made was good for the client. But when the the naming standards changed, it caused thousands of products to change names. This, in turn, updated the URLs of those product pages, triggering a 301 redirect on each page.

301-redirects

For example, when updating for the purpose of having a steady style, the merchandising team changed “bar stools” to the more accurate two-word version of the product name, “bar stools.” Wayfair had more than 8,000 bar stools, all of which 301-redirected to a new URL following the name change. Then, a couple of months later, the merchandising team found that they were getting good results by involving the height of the bar stool in the product name, so they updated the product names again, which resulted in the product pages 301-updating once more to a brand new set of URLs.

This procedure of updating product names was being implemented across dozens of different product classes, with many updates every month. It quickly added up to a lot of 301 redirects.

Measuring the impact

After reshaping our URL logic to prevent the steady redirects, we understood that we had a good opportunity to find out exactly how 301 redirects affect organic traffic. Nailing down data was easy. We had the exact dates of the changes; groups of thousands to millions of pages, with millions of organic visits; and could compare those classes against others that we knew didn’t change to exclude the impact of Wayfair’s overall increment in organic traffic.

We found with surprising consistency that we had a drop very near to 15% of organic traffic for any product class that changed URLs. In our bar stools example, we lost only under 15% of organic traffic at the 1st change. When the URL changed again over a month later, we lost another 15%.

301-redirects

Each product class we looked at showed the same drop within 1 to 2 weeks of the change. Sometimes the drop was almost immediate (like with bar stools); other times, however, it was spread out over several weeks (e.g., area rugs, with over 30,000 products).

We didn’t see any proof of recovery from the impact of the 301 redirects, even after numerous months. There was the appearance of recovery — class traffic levels eventually returned to where they began — but that was because our overall organic traffic was increasing across the whole website. We were still 15% below where we would have been without the redirects.

What’s especially fascinating about this number, 15%, is that it is precisely the amount of PageRank loss Google described in the original PageRank paper. So our measured results matched theory with surprising precision. Maybe the broader authority signals Google now measures follow the same logic for flowing through pages as they did in 1998? Or maybe it’s only a happy coincidence.

What it means

We’ve always known there was a “little” cost to implementing a 301 redirect, but our accidental SEO test demonstrated us that the cost is quite critical, and it becomes much greater with each hop in a redirect chain.

It’s worth stressing, however, that we are not saying that 301-redirecting any specific page is going to cost you 15% of your organic traffic. If you rank in position #1 for competitive terms, a redirect could drop you to position #2 or #4. That would cost you significantly more than 15% of your organic traffic. On the other hand, your page could be so strong that you may not see any loss in rankings after redirecting it.

What our information recommends is that, on average, there’s a 15% traffic loss following a 301 redirect; but any individual redirect could be vastly better, or much worse.

While 301-redirecting a dead or changed page to the new location is still great practice, the best practice of all is not to change your URL in the first place.