Yesterday, Google Webmaster Central provided some helpful guidelines around website testing and how to minimize the possible impact of A/B or multivariate website testing on a site’s performance in search results.
Google Webmaster Trends Analyst, Susan Moskwa, offered a “primer” on the different types of website testing and specified Google’s “guidelines for running an effective test with minimal impact on your site’s search performance.”
Here are Moskwa’s recommendations, taken directly from her post:
Cloaking, showing one set of content to humans, and a different set to Googlebot is against Google’s 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.
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).
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 have 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.
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Moskwa indicates that if you follow the guidelines and recommendations, your tests should have “little or no impact on your site in search results.” She also stated that if Google” crawl(s) your site often enough to detect and index your experiment, we’ll probably index the eventual updates you make to your site fairly quickly after you’ve concluded the experiment.”
The Webmaster Central Blog is a great way to stay on top of Google’s most recent changes and guidance. You can read Moskwa’s entire post and sign up to receive email notifications of new posts here.