Why Do My A/B Tests Cause Website Flicker?

By Mike Fradkin

October 3, 2023


A/B testing is an undeniably important tool in the world of website optimization, as most A/B testing programs yield an average 49% increase in conversions

However, some A/B testing solutions introduce website flicker with the addition of JavaScript Tags, giving customers a confusing experience on the webpage. When these less-than-ideal A/B testing solutions attempt to remove the flicker with delayed page load, they add latency, leaving viewers with an all-around frustrating experience. 

So it begs the question: should you have to sacrifice your potential profit gains from A/B testing to improve the customer’s webpage experience? A compromise in either direction will inevitably result in lost revenue, leaving you stuck between a rock and a hard place.  

In this blog, we’re going to uncover how your A/B testing platform sometimes causes website flicker and why you don’t need to compromise when you have the right solution at your fingertips. Ready to boost your loading performance while nailing your website experiments? Let’s get into it. 

What is Website Flicker?

Website flicker might sound like a minor annoyance, but it can be a real headache for both website owners and their viewers. It occurs when viewers navigate to a website, are shown the default experience or page, and then a personalization or A/B test variation of that page starts to load over it. For the user, this results in unexpected changes in how the page looks or functions. This issue exists when A/B testing and personalization solutions are being delivered by a tool that uses JavaScript tags. 

Imagine this scenario: A user clicks on a link to explore a product, and just as he/she starts reading about it, the entire page layout goes haywire or the colors shift dramatically. It’s disorienting. It’s confusing. It’s not the user experience you want to provide.

Website flicker can take various forms:

  • Content Shuffle: Elements like text, images, or buttons decide to play musical chairs, moving around or changing size as the page loads. It’s like trying to hit a moving target.
  • Color and Style Surprises: Suddenly, the website’s colors, fonts, or styling elements take on a whole new look. It’s a bit like redecorating a room when someone’s already in it.
  • Functional Hiccups: Interactive features, such as forms or menus, may decide to take a coffee break and not work properly, leaving users scratching their heads.

This less-than-ideal user experience can impact your website’s performance in various ways, from higher bounce rates to painfully lower conversion rates. It’s a situation that can make you feel like you’re fighting an uphill battle, especially if you’re grappling with an A/B testing solution that’s ill-equipped to handle this challenge. Let’s dig a little deeper into the underlying causes of this website flicker.  

Why does Website Flicker Occur?

You’ve experienced it, and now you know it could be a huge hurdle for your viewers. But why does website flicker even happen in the first place? 

The primary underlying cause of website flicker among many A/B testing solutions lies with the use of JavaScript (JS) Tags. The issue occurs when a default page is loaded and then a JS tag instructs a part of the page (or the entire page) to be rewritten with your test variation changes. 

Some A/B testing solutions try to mitigate the flicker effect by delaying the page load until the customized changes have taken effect, but this option adds latency. 47% of website viewers won’t wait longer than two seconds for your page to load. An additional 40% of viewers will leave your page if it hasn’t loaded in a mere three seconds. That’s 87% of your traffic lost as A/B testing solutions try to mitigate the flicker. 

Now that you understand the “why” behind website flicker, let’s take a look at the impact it could have on the folks landing on your flickering webpages. 

The Impact on the Customer Experience

Website flicker that occurs during A/B tests can have a major impact on the way your customers perceive and engage with your site.

When a potential customer hits your website with a specific goal in mind, they expect a smooth and cohesive user experience that guides them easily through your pages. 

However, when website flicker is present, this smooth journey is disrupted. Rapid changes in layout, color schemes, or even content can leave your visitors feeling frustrated—and rightfully so! Their initial trust in your website may waver, and their patience will definitely be tested. 

For e-commerce sites, this disruption could deter customers from completing their purchases, resulting in lost revenue. Even for informational websites, excessive flicker might lead to higher bounce rates as users abandon your site in search of a more stable and user-friendly alternative.

The bottom line is, website flicker can leave a lasting negative impression on your brand. Customers may associate your site and brand with a lack of professionalism or reliability, which can harm your reputation in the long run. It’s essential to remember that every interaction a user has with your website contributes to their overall perception of your brand.

A/B tests are valuable tools for optimizing your website, but they must be executed with care to ensure that they don’t disrupt the user journey. Balancing this optimization process with zero website flicker is possible—when you have the right solution on your side. 

The Impact to Your A/B Test Results

Flicker not only adversely affects your viewer’s experience, but it can also directly impact your A/B testing efforts in ways that you might not even be aware of. Let’s take a look at two examples:

False Winners

In this scenario, a viewer clicks on your page to find a blue button. But it suddenly shifts to purple. They click the button because of the flicker effect, leading you to believe you have a winning testing variation. But now that you’ve implemented this purple button as a global change, it performs poorly. Why? Because the unknown-to-you flicker effect manipulated the testing results. 

False Losers

This situation happens when the flicker effect is observed solely by the user exposed to the variation, leading to negative outcomes such as abandonment and delayed initial reactions. Surprisingly, these adverse consequences are often mistakenly attributed to the variation being tested, rather than recognizing the underlying culprit—the flicker itself. It’s essential to accurately identify and address the root cause to make informed decisions and optimize user experiences effectively. 

How to Avoid Website Flicker

Now that we’ve grasped the impact of website flicker—on your A/B tests and the customer experience—let’s look at how you can avoid it altogether. As we’ve mentioned, some A/B testing solutions try to mask the issue by delaying the page load—but this adds latency. 

Compared to our competitors, SiteSpect not only eliminates flicker, but our solution removes it without adding latency. Our transformation engine that sits in the flow of traffic is the secret sauce that enables flicker-free experimentation. Let’s take a closer look: 

1. Real-time Testing with Zero Flicker: SiteSpect’s real-time testing capabilities are a game-changer. Unlike traditional A/B testing tools that introduce flicker during experiments, SiteSpect ensures seamless transitions between variations. Your users won’t even notice the changes happening behind the scenes.

2. Instantly Deployable Changes: SiteSpect allows you to make changes on the fly. No need for extensive development or code deployments that could potentially disrupt your website. This agility means you can react quickly to market trends without the risk of flicker.

3. Client-Side Testing Without JS Tags: SiteSpect’s client-side testing capability is the secret sauce to flicker-free testing. Other client-side A/B testing platforms rely on JavaScript tags, which cause flicker and disrupt site performance, data quality, and scalability. But SiteSpect’s Find and Replace is the fastest, most robust A/B testing and optimization solution out there.

4. Server-Side testing and feature flagging: Our competitors offer server-side testing to beat website flicker. But what about the non-technical marketers who want to test without a developer? It means they have to compromise. We offer the same interface for either side—both flicker-free and ready for implementation. 

5. Comprehensive Visual Editor: SiteSpect’s Visual Editor simplifies the testing process. With this easy-to-use interface, you can make design and content changes effortlessly and test as much as you want without the worry of causing website flicker. 

By choosing SiteSpect as your A/B testing partner, you’re investing in a solution that not only understands the challenges of website flicker but also has the tools to overcome them effectively. Your users will silently thank you for the seamless experience, and your organization will greatly benefit from improved engagement and conversion rates.

Final Thoughts

Every second counts, and every visitor matters. We’ve learned that website flicker, a seemingly minor issue, can have a huge impact on your website’s performance and your users’ experience. It’s not just about losing precious seconds; it’s about losing potential customers and revenue.

But here’s the good news: You don’t have to compromise on load times or A/B testing. Our cutting-edge A/B testing platform offers a flicker-free solution that lets you optimize your website without disrupting your users’ journey. 

Ready to put an end to your website flickering woes? Request your personalized live demo of SiteSpect, and avoid the compromise. 


Mike Fradkin

Mike Fradkin

Mike Fradkin is the Director of Product Marketing at SiteSpect. His experience ranges from smaller series-A startup companies to large multinational corporations such as AT&T and IBM. With a technology career that began with several customer-facing leadership roles, Mike never loses sight of the connection between technology value and the real people it can positively affect. He enjoys the challenge of identifying trends and market drivers, truly understanding the problems of customers within their specific industries, cultures, and reporting structures, and leveraging those insights to deliver more impactful results.

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