A/B Testing Can Slow Down Your Website, Here’s How You Can Prevent It

AB testing
Digital Marketing |   February 1, 2022 by  Alekh Verma

A/B testing is one of those much popular ways that are used to increase conversion rates on a website.

Probably you too have used tools like Google Optimize for the same purpose.

Such tools are massively used to present website visitors with different variations of websites, randomly and find out which version performs the best.

A/B testing is also quite beneficial for saving your time and efforts in making developmental changes that might become unpopular among users. Although there are some drawbacks to A/B testing too.

It often leads to slowing down your website making the web pages take longer to load. Hence, website visitors get a slow user experience and that might lead to increasing bounce rates and less conversion.

This primarily happen if the content on your website is getting tested too often or your backend or frontend codes are used in such a way that is laying out a slow experience.

Although, no matter the reason, consequences will be similar.

So, if you too experiencing similar things with A/B testing and are concerned about these consequences, then worry no more as in this blog we will be discussing ways to prevent A/B testing from slowing down your website.

But before that let’s find out

How Does A/B Testing Slow Down Your Website?

Primarily, the lag in opening your website caused by A/B testing is because, there is an extra step involved in the process.

The reason behind this is nothing but the lag between back-and-forth communication which pushes back the loading speed of your website.

Yes, the versions that are shown to users are selected randomly and that is why data also gets collected on a real time basis regarding which of the versions is performing better. And, as that communication takes time, it gets added in the loading time of your website, causing a lag.

Another technical glitch called the flicker of original content can also take place while your website is loading. It is the appearance of the original content takes place before your website gets loaded completely.

There are three ways by which A/B testing can slow down your website. These are,

  • Increasing the loading time of your website
  • Giving a poor user experience leading to high bounce rates
  • Delaying events as the loading time gets increased and rendering gets delayed.

And, as you already know, your website’s loading time plays a crucial role in SEO and helping you get successful conversions.

Yes, according to stats, even a five second delay can make a great impact on your website’s conversion rates.

Also, a good lot of users claim that the loading speed of a website is quite important for them and that heavily influences their interest in buying from a particular website.

So, it is quite clear that if you want your users to stay on your website and buy from you, you need to make efforts to get your website loaded faster than ever.

How to Stop A/B Testing from Increasing the Loading Time of Your Website?

So, if you want to keep on A/B testing your website with letting it impact your website’s loading speed, then you need to make sure that you are taking necessary precautions.

There is a particular benchmark for website loading speed and you need to adhere by that in order to maintain your conversion rates.

Speaking of these benchmarks, Backlinko says, the average page loading time is 10.3 for desktops and 27.3 for mobile devices. So, yes, that is the time limit that you need to take care of.

So, now let’s take about the ways, the loading time of your website can be decreased eb match with the benchmarks.

  1. Add Scripts in the Top of the Head Tag

Developers often make the mistake of keeping the A/B testing scripts in a tag manager. And this makes a great deal of impact on the loading speed of your website.

To avoid such consequences, they should try keeping them on the top of a header tag.

Yes, the reason behind is, whenever you make certain changes to your website, the codes get overwritten.

Now, when you store your A/B testing scripts in a tag manager, which is an external script, it overwrites your newly written codes without warning and that prevents your scripts from performing their functions accurately.

However, if the synchronous version of the A/B testing codes is getting used in the process then it is your job to make sure that they are placed right after your website’s main scripts.

If you do this properly, then this arrangement of codes with help your website load faster, eradicating all sorts of delays caused by third-party resources that are present on your website.

  1. Use Animations to Improve User Experience

Animations are a great way to mask the high loading time of your website.

Yes, if you are performing A/B testing and it is making your website open slow, then you can make use of animations to prevent poor user experience caused by slow loading of your website.

Yes, using animations can really divert users into something while buying time for the website to take enough time to load properly.

While users wait for your website to load, an interactive animation can easily shift their focus and lift the feeling of boredom, bringing down bounce rates.

You can use animations like a loading bar that shows the progress of your website getting loaded, successfully preventing them from just hitting the back button and entering a website of your competitors’.

Place the animation somewhere, where your user will stay focused. And what can be better than a loading page popping up and showing the progress of your website.

But, while you do this, keep in mind to implement animations properly enough so that they do not end up interrupting other tests.

  1. Keep the Snippets Small

Adding snippets to a website is nothing new. A good lot of websites out there use snippets for various purposes.

But, if you are performing A/B testing on your website which causing it to open slowly, then snippets might even increase the loading time causing more harm to your conversion rate.

Hence, it is the best to keep your snippets as small as possible.

If you manage to keep your website snippets small enough, it will help snippets from slowing down other areas of your website.

This course of action will prevent other codes on your website to from getting slowed down or interrupted.

Google Tag Manager can prove to be enough helpful in performing this task. It is quite useful in shorted your snippets or just helping you include them on particular pages where they are necessary, instead of adding them in all pages of your website which leads to increasing the loading time of your website.

Although, while using Google Optimize for all the pages of your website, it is not necessary to use Google Tag Manager.

And, if you wish to embed the script for A/B testing directly on every single page of your website, then make sure that they are incorporated on the top of head tag as we have mentioned in our first point.

  1. Use Asynchronous Tracking

Google Optimize comes in two different versions. These are, synchronous and asynchronous.

The synchronous version of Google Optimize can make your website load slower as it stops all the content of your website from getting rendered until the synchronous script has loaded completely.

However, the asynchronous version of Google Optimize also stops content from getting rendered until it is completely ready, however, that happens independently and does not affect your website content’s loading speed.

Hence, we recommend using the asynchronous version. This is because the asynchronous version of Google Optimize loads separately without affecting the loading speed of your website and does not stop important tasks from getting executed independently before it itself gets loaded.

This version of Google Optimize does not slow down the animations on your website and can allow the other elements of your website to play before it has been loaded.

As mentioned earlier, we do not recommend using the standard version of Google Optimize, which is the synchronous version, instead you can just use any JavaScript Management System or any tag manager like Google Tag Manager, implementing it asynchronously.

Clearly, if you can manage doing this properly, then Google Optimize with not slow down the loading speed of your website. All you must do is adding it asynchronously to every script of your website.

It becomes a mandate when you do not happen to run any tests on your website or tests happen on all the pages of your website in a non-interruptive manner.

  1. Test on the Server-Side

The delay in loading time of your website becomes very subtle and unnoticeable when you conduct A/B testing on different server sides.

For instance, many website owners use PHP instead of the regular JavaScript Management System for A/B testing on their client’s side to eradicate the slow loading of website content and to make users experience their new website design seamlessly.

When you use the synchronous version of Google Optimize or any other tool that runs synchronous scripts, they prohibit a callback function from getting triggered which prevents your website content from loading before it has loaded completely.

However, in the case of asynchronous scripts on different server sides does not work the same way, which means, it does not prohibit browsers from blocking the callback function.

This is quite beneficial as testing on the server-side will prevent users who are accessing your website using slow network connections to face any such delays.

Although if you cannot perform this task on your website, then it is better to use the technique mentioned in point no. 4, i.e., using Google Tag Manger with asynchronous scripts which makes you’re a/B testing scripts load separately and do not affect the regular loading speed of your website.

The main problem with testing on a server-side is that it often becomes difficult to get the job done as it not possible to call asynchronous JavaScript into action.

  1. Keep All Data in a Single File

There are lots and lots of data and assets on your website that need to get loaded completely before the website is visible to a user.

While running A/B testing on your website, these huge amounts of data and assets get shared between two experiences but, this sharing can cause a good lot of issues if the data and assets are not managed properly.

Let’s say, your old website used to use some other fonts that were not so web friendly, so, you used Google Fonts in your new website. Now, while performing A/B testing on your websites, your old website should also be using Google fonts.

Now, if this font related assets are not managed properly, there will be a significant delay in the loading speed of your website as all these data and assets get loaded on top of each other.

Here what you can do to manage this issue is keeping all your data in a single file so that the A/B testing does not slow down the loading of your website. This will eradicate the chances of your website from making multiple requests for necessary information.

Make sure that all your experiments are stored in a single folder so that so that every member of your team can access them easily. This also prevents a good lot of issues from occurring and makes tracking the progress and performance of your website a lot easier to measure.

  1. Combine and Optimize Variation Code

Variation codes are used by Google Optimize to run A/B testing for each of variations of your website. So, consolidating and optimising the variation of these codes can easily prevent A/B testing from bringing down the loading speed of your website.

The number of variation codes you need to create and the frequency of running these A/B testing depends on how complicated your website is. And that’s why the loading speed of your website gets slowed down.

Now if the number of changes applied to a particular website is too high then that event prevents the other scripts of the website to running properly or may even prevent the entire page from loading.

This will end up being extremely harmful for the experience that any user gets while visiting that particular website. It may also stop you from optimising your website too.

Supposedly, if your website does not have a JavaScript Management System, or does not have it activated, then A/B testing will never reach that particular variation of your website which contains optimised content. In worst cases, it might even stop optimisations for weeks, which will end up being very harmful for your website.

This is why having your optimised variation codes combined at the top of your header tag so important for website.

Final Thoughts

A/B testing is a great way to increase conversions and bringing down bounce rates if done appropriately. Also, this is such a technique that every website owner should try out.

But, for that you need to know how you can prevent it from slowing down the loading speed of your website as it will end up giving your website visitors very poor experiences and that will shoot up the bounce rates.

So, it is quite important to utilise the above-mentioned ways to take complete advantage of A/B testing and increase your website traffic and successful conversions.

About the author

Alekh Verma

A Search Engine Optimization specialist known for his bold and insightful approach to every web industry trend, Alekh Verma is a proud Founder and CEO of a successful Digital Marketing, Mobile App, and Web Development firm, eSearch Logix Technologies. His practical and inventive ideology has helped to shape the success story of his firm, which has now grown into a thriving, leading digital marketing company based in NCR, India. He brings a global perspective to the industry and has helped multitudes of businesses across the globe from all sectors create an impactful presence in the virtual world.


A/B Testing, Website loading time optimization, Website speed optimization

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