What is SEO Split Testing

AB testing


A / B tests (sometimes referred to as split tests) compare two versions of a web page to determine which version is more suitable for achieving a defined goal. Such a goal can be, for example, increasing the conversion rate or improving other performance indicators (KPIs). An A / B test compares two website versions by randomly directing visitors to one of the two versions and recording user behavior. This allows webmasters and companies to test how much the behavior of visitors is influenced by changing a certain variable.

The goal of A / B testing

The goal of A / B testing is to find the best possible website version to achieve a specific goal and to learn what changes can be used to get more visitors to a website to do something they want.

Compared to the cost of paid traffic, the cost of increasing the conversion rate using A / B testing is minimal. The return on investment from A / B testing can be very high, as even small changes to a website can lead to significant increases in leads and sales generated.

How A / B tests work

Illustration: AB Testing - Author: Seobility - License: CC BY-SA 4.0

In an A / B test, a second version of a website is created in which a certain element that is to be optimized is changed. This change can, for example, affect a heading, a button, images or colors. Rarely does the change involve a complete redesign of the page.

In the next step, half of the visitors are directed to the original version of the page, which is used for control, and the other half to the modified version of the page. The behavior of the visitors is measured and analyzed on both sides. In this way, it can be determined whether the change had a positive, negative or no influence on visitor behavior (for example with regard to the conversion rate).

Application examples for A / B tests

Application examples for A / B testing are the optimization of landing pages, mails or e-commerce pages with regard to conversion rate, leads, registrations, etc. The following elements, among others, can be changed and examined:

  • CTA buttons: size, shape, text, color and placement
  • CTA texts: length, content and formatting
  • Headings: content, length, font size, typography
  • Texts: length and content
  • Images: static or carousel, size and placement

Pros and cons of A / B testing

A / B testing is very suitable for testing new ideas and determining whether they lead, for example, to an improvement in the conversion rate, a reduction in the bounce rate or an increase in the length of stay. Possible changes can be checked step by step and tested on one side. This makes it possible to check in a comprehensible way whether different colors, buttons, layouts or images influence the behavior of the visitors.

A disadvantage of A / B tests, however, is the time it takes to prepare and set up two different versions of a website.

For websites with little traffic, the tests may also have to be carried out over several weeks or months in order to obtain a sufficiently large database for meaningful results.

A / B testing also cannot measure or indicate whether there are usability problems on a website that could be responsible for a low conversion rate.

Additionally, changing multiple variables at the same time creates the risk of misinterpreting the results of the test.

A / B testing tools

A whole range of professional, partly free and partly paid tools for A / B testing is available on the Internet:

Google Analytics - Experiments

The "experiments" of Google Analytics make the tool a complete A / B test platform. Users can split test up to 10 full versions of a single page here.


KISSmetrics is a powerful analysis platform. The KISSmetrics JavaScript library offers a function that assists users in setting up their A / B tests. Users can also integrate KISSmetrics into their internal test code or into another A / B test platform.


With Unbounce, responsive landing pages can be created, published and tested without any knowledge of HTML. Unbounce can be integrated with a variety of other tools. The tool also offers the possibility of assigning roles to team members, capturing leads and integrating videos, social feeds and widgets to optimize the conversion rate of a website or email.


Optimizely is one of the most popular WYSIWYG A / B testing tools. Optimizely enables tests based on ad campaign, geography or cookies to facilitate the design and optimization of personalized content based on target group segments.

A / B testing in terms of search engine optimization

Google allows and encourages webmasters to do A / B testing and has stated that running an A / B or multivariate test does not pose an inherent risk to a website's ranking. However, it is possible to jeopardize the ranking if A / B testing tools are misused. So Google recommends that webmasters do the following to ensure this doesn't happen:

A / B tests should generally not be misused for cloaking. Cloaking means that search engine crawlers are deliberately directed to a different version of the website than the user in order to fool the search engine. But even if webmasters have no such intentions, they should be careful not to fundamentally change the content of a page in the context of A / B tests. If Google finds that the variation of a page differs significantly from the original not only in terms of design, but also in scope and content, Google could misunderstand this change as cloaking and the website may face a penalty. For this reason, an A / B test should never last longer than necessary, as Google could also perceive this as an attempt at deception.

Canonical tags should also be used in A / B tests to refer to the original page if the A / B test has several URLs.

Setting up 302 redirects isn't harmful as long as it doesn't redirect to unexpected or unlinked content. 301 redirects, on the other hand, should not be used, as they would signal Google that a permanent redirect is unusual in A / B tests.

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