{"id":112047,"date":"2023-05-25T09:00:02","date_gmt":"2023-05-25T09:00:02","guid":{"rendered":"https:\/\/staging.wingify.com\/blog\/client-side-to-server-side-testing\/"},"modified":"2026-09-03T16:38:21","modified_gmt":"2026-09-03T11:08:21","slug":"client-side-to-server-side-testing","status":"publish","type":"post","link":"https:\/\/wingify.com\/blog\/client-side-to-server-side-testing\/","title":{"rendered":"When to Make the Leap from Client- to Server-Side Testing"},"content":{"rendered":"

As companies start out their experimentation<\/a> journey, they may find themselves experimenting with small changes on their website such as the design of a CTA and other small changes to explore how they perform and their impact on <\/span>key KPIs<\/span><\/a> such as conversion rate and transaction.<\/span><\/p>\n

However, as an experimentation program matures, companies are more likely to want to delve deeper into more sophisticated types of testing which require more expertise and a more advanced tool.<\/span><\/p>\n

This is the point when many companies are ready to take the plunge from client- to server-side experimentation.<\/span><\/p>\n

In this article, we will explore when is the right time to make the shift to server-side testing and discuss the importance of running these types of tests by outlining the various scenarios where server-side experiments are more appropriate.\u00a0<\/span><\/p>\n

Client- <\/b>\u00a0<\/span>vs server-side testing<\/b><\/h2>\n

Before we go deeper into server-side testing, we will quickly point out the differences between client- and server-side tests to understand why you need both types of testing as your experimentation and optimization program evolves.<\/span><\/p>\n

In client-side testing is where experimentation occurs on the client side through Javascript that runs in the browser. Therefore, client-side tools enable you to create variations of your pages by changing the content sent by your server to users in the web browser. The user then gets one variation of your altered content based on your targeting rules.<\/span><\/p>\n

Put simply, all the work happens at the level of the browser thanks to Javascript. Because of this, <\/span>client-side testing is usually best for surface-level changes such as layout, design and colors<\/b> to measure their performance and impact on key KPIs.<\/span><\/p>\n

Meanwhile,<\/span> all the work in server-side testing happens at the server level rather than the browser.<\/b> In other words, it\u2019s your server that randomly sends a user the modified variation. As a result, the experimentation tool works on the server instead of inside your users\u2019 browsers.\u00a0<\/span><\/p>\n

Perhaps one of the biggest benefits of client-side tests is that it\u2019s easy to implement and no special expertise is required to run these tests on the front-end of the website.<\/span><\/p>\n

However, because of its advanced capabilities, server-side tests require technical expertise\u00a0 and coding skills and so developers are usually the ones running these tests on the back-end.\u00a0\u00a0<\/span><\/p>\n

What are the benefits of server-side testing?<\/b><\/h2>\n

Before we go into when you should be using server-side tests, we will outline some of their benefits in order to better understand their use cases.<\/span><\/p>\n

Omnichannel experimentation<\/b><\/h3>\n

Client-side solutions are usually limited to devices with web browsers, whether that\u2019s on desktop, mobile or tablet. This means you cannot run experiments on mobile apps or connected devices.<\/span><\/p>\n

Server-side solutions, for their part, allow you to experiment across multiple channels including mobile apps which significantly widens your playing field and opens up numerous opportunities to A\/B test beyond web browsers so you can cover all your bases.<\/span><\/p>\n

Enhanced performance<\/b><\/h3>\n

Perhaps one of the biggest advantages of server-side tests is the absence of the flicker effect, which is often a major downside associated with client-side solutions. \u00a0<\/span><\/p>\n

The <\/span>flicker effect<\/span><\/a> occurs when the original page loads and is replaced by the test variation and is usually seen by the user.<\/span><\/p>\n

Unlike client-side tools that require adding a Javascript tag to your pages, you don\u2019t need to add this tag in server-side tools. That\u2019s because experiments are rendered on the server before being pushed to the client and so all the major work occurs at the server level- it\u2019s not noticeable on the client side.\u00a0<\/span><\/p>\n

In other words, during a server-side test, the variation is retrieved from the server and delivered to the user\u2019s browser. As a result, no modifications take place on the front-end or browser, so there\u2019s no flickering effect<\/span><\/p>\n

Endless testing opportunities<\/b><\/h3>\n

Your teams have a lot more options to work with when it comes to server-side testing as it enables you to modify all aspects of your site.<\/span><\/p>\n

As server-side tests are rendered from the back-end server, <\/span>you can test more complex dynamic content<\/b> unlike with client-side tests where it\u2019s not easy to test such content and may damage the user experience if done on the client-side.\u00a0<\/span><\/p>\n

In other words, you can build tests that are much more complex that go deeper within your tech stack beyond the scope of UI or cosmetic changes to unlock a whole new world of experimentation.\u00a0<\/span><\/p>\n

With such deep experimentation capabilities, <\/span>teams can thoroughly test all facets of a product<\/b> to validate its functionality such as evaluating its underlying features, algorithms and back-end logic.\u00a0<\/span><\/p>\n

The next section will go over these various use cases where you should consider running server-side testing instead.<\/span><\/p>\n

When does it make sense to move to server-side testing?<\/b><\/h2>\n

As we\u2019ve mentioned, server-side tests are usually used to run more advanced types of tests and experiment deeply within your tech stack to thoroughly explore how a product works.<\/span><\/p>\n

Put simply, <\/span>server-side experimentation solutions allow teams to conduct more robust and secure experiments that are focused on modifying a product\u2019s functions.\u00a0<\/b><\/p>\n

Here are some use cases where server side testing is recommended over client-side testing:<\/span><\/p>\n