Tip of the Week: A/B testing

A/B testing without page flickering and loading delay

These four best practice tips help managing key challenges when playing out A/B tests:

1. Use asynchronous code by default

As a general rule, we recommend playing out the etracker code asynchronously – as provided by default. This ensures optimal website speed, which is beneficial for the user experience and Google ranking. In particular, it prevents the consequences of a ‘worst case scenario’: the loading delay of the website when the etracker services are overloaded.

2. As high up as possible in the <HEAD> area of the HTML code

The etracker code should be placed as high up as possible in the <HEAD> area of the website’s HTML code. This ensures the best possible data collection in web analysis and minimises possible flickering effects in A/B testing. The earlier the etracker code is executed, the faster it is possible to check whether the conditions for a test or smart messaging campaign apply and to play it out.

3. Activate optimiser only on pages with campaigns.

For the setup and playout of A/B tests or smart messaging, an additional parameter must be added to the tracking code in the parameter block on the corresponding web pages: data-enable-eo=”true”. If this is set, a white layer is placed over the page before it is displayed. It is removed when the variant becomes visible through injection or redirection (at the latest after 300 milliseconds or 0.3 seconds – configurable via parameter). This prevents the original page from being displayed during the loading time. If no test or smart messaging project is active or in preparation, this is of course unnecessary.

4. Tests with major changes in the directly visible area

The check before loading a variant usually takes only a few milliseconds. Nevertheless, this can lead to flickering effects if the page loads very quickly. This means that the page is briefly displayed in the original and then fades out until the test change is applied. In such cases, it can make sense to use the synchronous code option. Advantage: the risk of flickering effects is minimised. Disadvantage: the loading time can be affected, as the page is only (re)loaded after a response from the etracker server.

Alternatively, sequential tests can be carried out and evaluated as an onsite campaign in etracker Analytics. To do this, simply add suitable parameters for onsite campaigns to the URL when playing out the test variants:


Optionally, the URL can be created using a link generator:

The success can be evaluated under Marketing Reports → Onsite Campaigns by comparing the effect on engagement and conversions. If the variations are played out one after the other, care should be taken to ensure that the time periods are as comparable as possible and that the results are significant. For the latter, https://www.surveymonkey.com/mp/ab-testing-significance-calculator/ can be used, for example.

Conversion optimisation by means of A/B testing is therefore also highly practicable in times of loading time as a ranking factor.

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