How and When to Use 301 Redirects vs. Canonical

301-redirect-canonicalWeb page redirection can seem like a bit of a minefield. The 301 redirect and canonical options have been around for years, but they tend to create confusion and consistently stir-up questions and debate on best practices.

This post will focus on the two main methods of managing the redirection of a single page on your website – the 301 redirect and the rel="canonical" attribute – to conquer duplicate content issues, sustain your rankings, and improve user experience.

What's The Difference?

Though there are a few gray areas, Google provides some clear guidelines to make sure we all know how they want us to manage redirections. In very simple terms, here is what each communicates to Google and search engines:

301 – Hey, Search Engines: My page is no longer here, and has permanently moved to a new page. Please remove it from your index and pass credit to the new page.

Canonical – Hey, (most) Search Engines: I have multiple versions of this page (or content), please only index this version. I'll keep the others available for people to see, but don't include them in your index and please pass credit to my preferred page.

Now, let's get into some of the details…

301 Redirects

The 301 HTTP status code has always been the standard for managing the complete and permanent redirection of a page. By implementing this command you will be eventually pass the majority of the original page's link authority, relevance and ranking power to the page you are redirecting to. Google's Distinguished Engineer Matt Cutts has said, you'll lose "just a tiny little bit, not very much at all" which "doesn't change over time".

The 301 tells both users and search engines that your original page is no longer relevant and that the most relevant and up to date information can be found on your new page.

Sounds simple enough, right?

Common Problems with 301

There are a few possible problems with implementing a 301 redirect.

First, it might not be possible for you to implement HTTP status codes. Maybe you don't have FTP access, or perhaps your web designers have told you it isn't possible. Either way, without server-side access, a 301 simply isn't an option.

Another possible downside of the 301 is that it does sometimes take a while for the search engines to attribute your new page with the search authority of your original page. This all depends on how often your site, and the original page, is crawled by the search engines. This delay means that a 301 is something you should never rely on for short term or last minute campaigns.

Finally, the most common problem is the 301 being used incorrectly. It's surprisingly common to see marketers develop a completely new site and then use a 301 to point all the pages of the original website to new site's homepage. This isn't what the 301 is intended for. This approach undermines the relevancy of any search traffic and could result in a very high bounce rate. It's a lose/lose situation and unfortunately, this is just one example among many.

Don't let these issues put you off. A 301 redirect is still the clear choice for permanent page redirection in most cases.

When to Use 301

  • As default – this is the preferred method
  • Pages that are being permanently moved or replaced
  • Domains that are permanently moved (acquisitions, rebranding, etc.)
  • 404 pages and expired content (assuming relevant content or a page exists)

The rel="canonical" Attribute

The rel="canonical" attribute, though it is often incorrectly used as a 301 substitute, is something entirely different. Rather than physically sending users to a more recent or relevant page, rel="canonical" is a signal that's purely for the benefit of the search engines.

There are often situations where you may have a number of web pages with either very similar or identical content. We all know that duplicate content is dangerous territory, so that's when to use the rel="canonical".

Let's say you have two (or more) pages both listing the same series of products. One lists them alphabetically and the other by price. They contain the same content, but have different URLs. If you were to leave both pages alone, Google would index both, but pick which one it believes is the most relevant and could filter the page you actually want to be appearing in the SERPs.

By placing rel="canonical" on the alphabetical page telling the search engines that the price page is your preferred choice, you avoid all these issues. This tells the search engines that you acknowledge that the content on these two pages is very similar and that the pricing page is the most important for users.

Regarding the amount of PageRank or link juice that would be lost from canonical redirects, Cutts has also said "there's really not a whole lot of difference" between the 301 and the canonical. This means the 301 and the canonical will lose "just a tiny little bit, not very much at all" of credit from the referring page.

To reinforce this, the Google Webmaster Central Blog states "Additional URL properties, like PageRank and related signals, are transferred as well."

Common Problems with Canonical

As with the 301 redirect, there are some limitations to rel="canonical".

First, it's only a suggestion. Though the major search engines all state that they do pay close attention to rel="canonical", they aren't obliged to follow them. This means that you may still see your ‘duplicate' pages occasionally being shown ahead of your preferred page in some SERPs.

Again, the biggest problem with rel="canonical" is how commonly it is misused. The most common misuse of the tag is when it's implemented on pages that don't include a large percentage of the same content as the canonical page. Unless they contain considerable chunk of duplicate content, rel="canonical" probably shouldn't be used.

Another common misuse of the tag occurs with multiple, related pages. For example, you might have written a long blog post on your site that you've decided to break up into five parts. Each of these parts is on a separate page with its own unique URL.

I've seen so many cases where each of these pages contains a rel="canonical" tag pointing back to the first page in the series. Though the right intention was there, using rel="canonical" tells the search engines that the content on each of these pages is almost identical and that you want it to always show the first page in the SERPs.

By using the tag you will stop pages 2-5 from ever being shown in the SERPs, even if they carry a high level of relevance and authority for that specific search. You're limiting your visibility, causing confusion, and creating unnecessary work for yourself.

In this instance, using pagination features with Rel="next" and Rel="Prev" tags. You can learn more about them here.

When to use Canonical

  • When 301s can't be implemented, or take too much time
  • Duplicate content but you want to keep both pages live
  • Dynamic pages with multiple URLs of a single page (from sorting features, tracking options, etc.)
  • Site-wide considerations like (domain/page/index.html vs. domain/page/ for the same page) can be easier with canonicals
  • Cross-domain considerations where both sites are similar, but need to remain live

Summary

Redirect options can be intimidating, but hopefully now you have greater clarity on the best course of action. Both options will pass a similar amount of link juice, and will be treated similarly by Google. But in general, the 301 redirect is the preferred route.