Google: A/B Testing? Don't Cloak, Use 302s & Use Rel Canonicals

I covered this at Search Engine Land last night, but it is worth covering here as well.

When you do any A/B testing or Multivariate testing with your web pages or web site, it is important that you do not confuse GoogleBot. If Google thinks you are breaking their guidelines or they just think something is off, it can have serious repercussions on your search rankings.

Susan Moskwa wrote a detailed blog post on how you can do A/B testing or Multivariate testing and reduce the risk of losing rankings in Google. In short, she said do not cloak, use 302 redirects (not 301s), use the rel="canonical" attribute and do not run the test for too long.

Here is her advice:

• No cloaking.
  Cloaking—showing one set of content to humans, and a different set to Googlebot—is against our Webmaster Guidelines, whether you’re running a test or not. Make sure that you’re not deciding whether to serve the test, or which content variant to serve, based on user-agent. An example of this would be always serving the original content when you see the user-agent “Googlebot.” Remember that infringing our Guidelines can get your site demoted or removed from Google search results—probably not the desired outcome of your test.
• Use rel=“canonical”.
  If you’re running an A/B test with multiple URLs, you can use the rel=“canonical” link attribute on all of your alternate URLs to indicate that the original URL is the preferred version. We recommend using rel=“canonical” rather than a noindex meta tag because it more closely matches your intent in this situation. Let’s say you were testing variations of your homepage; you don’t want search engines to not index your homepage, you just want them to understand that all the test URLs are close duplicates or variations on the original URL and should be grouped as such, with the original URL as the canonical. Using noindex rather than rel=“canonical” in such a situation can sometimes have unexpected effects (e.g., if for some reason we choose one of the variant URLs as the canonical, the “original” URL might also get dropped from the index since it would get treated as a duplicate).
• Use 302s, not 301s.
  If you’re running an A/B test that redirects users from the original URL to a variation URL, use a 302 (temporary) redirect, not a 301 (permanent) redirect. This tells search engines that this redirect is temporary—it will only be in place as long as you’re running the experiment—and that they should keep the original URL in their index rather than replacing it with the target of the redirect (the test page). JavaScript-based redirects are also fine.
• Only run the experiment as long as necessary.
  The amount of time required for a reliable test will vary depending on factors like your conversion rates, and how much traffic your website gets; a good testing tool should tell you when you’ve gathered enough data to draw a reliable conclusion. Once you’ve concluded the test, you should update your site with the desired content variation(s) and remove all elements of the test as soon as possible, such as alternate URLs or testing scripts and markup. If we discover a site running an experiment for an unnecessarily long time, we may interpret this as an attempt to deceive search engines and take action accordingly. This is especially true if you’re serving one content variant to a large percentage of your users.

One thing she adds is that if you follow the recommendations above then it should have "little or no impact on your site in search results." But she goes on to explain that there may be an impact do to content changes.

Forum discussion at WebmasterWorld.

Image credit to ShutterStock for comparing image