The impact on CRO and A/B Testing - Cookieless Series Part 6 | Articles

In this 6th article of our Cookieless world series that was highlighted already shortly in the previous article ‘How to prepare your digital marketing efforts towards a cookieless world - Cookieless Series Part 2’ we are looking deeper into the future of conversion rate optimisation and A/B testing.

As cookies are also leveraged by A/B testing tools, what will the impact on those tools be in the future? Are there alternative solutions at hand?


The impact of third-party cookies phase-out

Today, many advertisers have been building, some large scale and some small scale, units within their organisation that are focusing on improving the customer’s experience and journey towards conversion on their websites or other products. This with the purpose of driving bottomline business impact. Within this process, often referred to as conversion rate optimisation (CRO), a large importance is given to the use of a framework allowing for continuous testing and learning. Being able to test multiple variations of, for example, pages structures, designs and other elements, allows for identifying those elements that make the user’s experience easier and more pleasant. 

Within the CRO expert’s toolkit one tool is especially crucial. This is the A/B testing tool which allows the CRO team to test their hypotheses and test multiple variations against each other. Plenty of these tools exist on the market today. To name a few, there is Google Optimize, Optimizely, AB tasty, VWO or Adobe target and many more. 

Most of these tools have one specific element in common: they often rely on cookies to split up testing groups into test and control groups. The cookie serves here as a way to identify if a user should be shown variant A or variant B within a test whenever they are visiting our website. This identification process is crucial within a testing environment as we would not want users to be both seeing variant A and B. Thus, overlap could cause pollution in our test/control group and potentially bias the results of the test. 

Knowing now that A/B testing tools, so crucial in the optimization of our products, are relying so heavily on cookies, what will happen if cookies disappear tomorrow? How to run effective testing without cookies?


How does server-side testing work? 

As it was already highlighted in one of the previous articles on server-side tagging, use of server-side tag management can be made in order to circumvent the cookie dependency of today. This is also the case for A/B testing. 

Server-side testing is a method of A/B testing where the variations of a test are made directly on the web server and then rendered the same to the visitor’s browser. This differs from client-side testing, where the test is rendered on the client-side through JavaScript and the changes are only happening in the visitor’s browser. 

Server-side testing is more robust as it allows to run complex and advanced tests (for example testing changes like a database query result set), while client-side testing deals with simpler, design and UI-related tests (for example testing headlines or button colors). As server-side testing can handle more complexity, the implementation is also more technical and requires significant coding skills, as opposed to the implementation of client-side testing which is easier.

Today more and more businesses are moving from client-side testing to server-side testing, for reasons including page load performance, data control, etc. But also, and most importantly, is that it allows relevant user data for A/B testing to be persisted in the form of first-party, server-side cookies.

publication author justine heeren
Justine Heeren

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