{"id":44,"date":"2022-03-02T07:01:02","date_gmt":"2022-03-02T07:01:02","guid":{"rendered":"https:\/\/vwo.com\/glossary\/client-side-testing\/"},"modified":"2025-11-26T09:03:46","modified_gmt":"2025-11-26T09:03:46","slug":"client-side-testing","status":"publish","type":"post","link":"https:\/\/vwo.com\/glossary\/client-side-testing\/","title":{"rendered":"Client-Side Testing"},"content":{"rendered":"\n<h2 class=\"wp-block-heading\">What is client-side testing? <\/h2>\n\n\n\n<p>Client-side testing is the experimentation process of rendering variations at the browser level.&nbsp;<\/p>\n\n\n\n<p>When a user visits a webpage on a browser, it initiates a request to the server, which sends the required file to the browser. The browser then processes the file and displays the webpage. The interactive elements of the webpage are made possible through the use of JavaScript within the files.&nbsp;<\/p>\n\n\n\n<p>JavaScript is also used to generate variations for experimentation like A\/B tests, multivariate tests, and split tests. The JavaScript can be run at the browser level or the server itself. The JavaScript runs at the browser level for client-side testing, while the process of rendering the variations on the server is called <a href=\"https:\/\/vwo.com\/glossary\/server-side-testing\/\">server-side testing<\/a>.<\/p>\n\n\n\n<p>A use case of client-side testing is delivering <a href=\"https:\/\/vwo.com\/blog\/call-to-action-buttons-ultimate-guide\/\">call-to-action (CTA) button<\/a> variations for an A\/B test. Once a user becomes part of the A\/B test, the DOM selectors identify the HTML element (in this case, the CTA button), then execute the JavaScript at the browser to modify CTA and create variation. The modification can be anything like changing CSS style, hiding, removing, resizing, and duplicating.&nbsp;<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Advantages of client-side testing <\/h2>\n\n\n\n<p>Here are the benefits of client-side testing:<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Easy to adopt<\/strong><\/h3>\n\n\n\n<p>There are client-side <a href=\"https:\/\/vwo.com\/blog\/ab-testing-tools\/\">A\/B testing tools<\/a> like <a href=\"https:\/\/vwo.com\/why-us\/technology\/visual-editor\/\">VWO that offer a WYSIWYG editor<\/a>, which doesn\u2019t require coding to create variations. Such testing frameworks make it easy to adopt client-side testing, especially if the company is small and can&#8217;t afford a development team.&nbsp;&nbsp;<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Low investment cost<\/strong><\/h3>\n\n\n\n<p>It requires less financial investment compared to server-side testing. Client-side testing is a preferred mode of experimentation for businesses that are on a budget crunch or new to optimization.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Ability to test often<\/strong><\/h3>\n\n\n\n<p>Client-side testing allows for intuitive tools to create variations, which makes it easy for the CRO team to create variations frequently and test more hypotheses.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Limitations of client-side testing <\/h2>\n\n\n\n<p>Here are the limitations of client-side testing:<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>May reduce the website speed<\/strong><\/h3>\n\n\n\n<p>The JavaScript runs at the browser level, which increases the LCP (Longest contentful paint) time compared to server-side rendering.&nbsp;&nbsp;<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Flickering<\/strong><\/h3>\n\n\n\n<p>In client-side testing, a flash of original content appears before the variations, which is called the flicker effect. It may occur when the browser loads the variations by running JavaScript.&nbsp;<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Limited to UI\/UX testing<\/strong> <\/h3>\n\n\n\n<p>The JavaScript runs at the browser end, which is why there is a limit to the scope of experimentation. Complex experimentation like product search algorithm test is not feasible with client-side testing. Thus, complex and dynamic experimentation is possible only via server-side testing.&nbsp;<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Cannot run omnichannel experiments<\/strong><\/h3>\n\n\n\n<p>Client-side tests cannot run on the web and app at the same time. For omnichannel experiments, <a href=\"https:\/\/vwo.com\/server-side-testing\/\">server-side experimentation<\/a> is suitable.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Lifecycle of the client-side testing <\/h2>\n\n\n\n<p>Client-side testing involves multiple stages, which are as follows:<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>a. Behavior analysis<\/strong><\/h3>\n\n\n\n<p>Optimization starts with understanding the existing user flow and behavior. Typically, behavior analysis involves studying visitor data on analytics tools, analyzing <a href=\"https:\/\/vwo.com\/glossary\/dynamic-heatmap\/\">dynamic heatmaps<\/a>, understanding funnel journeys, and watching session recordings.&nbsp;<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>b. Creating hypothesis<\/strong><\/h3>\n\n\n\n<p>Based on the behavior analysis, a hypothesis that highlights the element for experimentation and the expected effect on a KPI is formulated.&nbsp;<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>c. Client-side testing<\/strong><\/h3>\n\n\n\n<p>Client-side A\/B or multivariate test is conducted to track and compare the performance of the variation to the original page called control. The experimentation ends with a winner. One important thing to note here is that <a href=\"https:\/\/vwo.com\/glossary\/multi-armed-bandit-testing\/\">multi-armed bandit testing<\/a> is gaining popularity because it exposes the traffic to better-performing variation with time before the test reaches statistical significance.&nbsp;<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>d. Deploy<\/strong><\/h3>\n\n\n\n<p>In the end, the winning variation is deployed on the live website exposing all the visitors to the new experience.&nbsp;<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>e. Documentation<\/strong><\/h3>\n\n\n\n<p>The whole process of client-side testing is documented with learnings, rectified mistakes, and results. It acts as a reference for future optimization campaigns.&nbsp;<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Summary <\/h2>\n\n\n\n<p>To summarize, client-side testing involves rendering experimentation variations at the browser level using JavaScript to modify elements like call-to-action buttons. It is easy to adopt, has a low investment cost, and allows for frequent testing, but it can reduce website speed, causing flickering, and is limited to UI\/UX testing.\u00a0<\/p>\n\n\n\n<p>The lifecycle of client-side testing involves behavior analysis, creating a hypothesis, client-side testing, and deployment of the winning variation. Complex and dynamic experimentation is feasible only via server-side testing.<br>You can start client-side testing with VWO. Know more about the pricing on the <a href=\"https:\/\/vwo.com\/pricing\/\">plans and pricing page<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Client-side testing is the experimentation process of rendering variations at the browser level. <\/p>\n","protected":false},"author":737,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[],"class_list":["post-44","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v26.9 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Client-Side Testing | VWO<\/title>\n<meta name=\"description\" content=\"Client-side testing involves rendering experimentation variations at the browser level using JavaScript to modify elements like call-to-action buttons.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/vwo.com\/glossary\/client-side-testing\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Client-Side Testing | VWO\" \/>\n<meta property=\"og:description\" content=\"Client-side testing involves rendering experimentation variations at the browser level using JavaScript to modify elements like call-to-action buttons.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/vwo.com\/glossary\/client-side-testing\/\" \/>\n<meta property=\"og:site_name\" content=\"VWO Glossary\" \/>\n<meta property=\"article:published_time\" content=\"2022-03-02T07:01:02+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2025-11-26T09:03:46+00:00\" \/>\n<meta name=\"author\" content=\"Aastha Trehan\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\/\/vwo.com\/glossary\/client-side-testing\/#article\",\"isPartOf\":{\"@id\":\"https:\/\/vwo.com\/glossary\/client-side-testing\/\"},\"author\":{\"name\":\"Aastha Trehan\",\"@id\":\"https:\/\/vwo.com\/glossary\/#\/schema\/person\/95c6d9ae0e137e8e23a76689292da18b\"},\"headline\":\"Client-Side Testing\",\"datePublished\":\"2022-03-02T07:01:02+00:00\",\"dateModified\":\"2025-11-26T09:03:46+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\/\/vwo.com\/glossary\/client-side-testing\/\"},\"wordCount\":743,\"inLanguage\":\"en-US\"},{\"@type\":\"WebPage\",\"@id\":\"https:\/\/vwo.com\/glossary\/client-side-testing\/\",\"url\":\"https:\/\/vwo.com\/glossary\/client-side-testing\/\",\"name\":\"Client-Side Testing | VWO\",\"isPartOf\":{\"@id\":\"https:\/\/vwo.com\/glossary\/#website\"},\"datePublished\":\"2022-03-02T07:01:02+00:00\",\"dateModified\":\"2025-11-26T09:03:46+00:00\",\"author\":{\"@id\":\"https:\/\/vwo.com\/glossary\/#\/schema\/person\/95c6d9ae0e137e8e23a76689292da18b\"},\"description\":\"Client-side testing involves rendering experimentation variations at the browser level using JavaScript to modify elements like call-to-action buttons.\",\"breadcrumb\":{\"@id\":\"https:\/\/vwo.com\/glossary\/client-side-testing\/#breadcrumb\"},\"inLanguage\":\"en-US\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\/\/vwo.com\/glossary\/client-side-testing\/\"]}]},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\/\/vwo.com\/glossary\/client-side-testing\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\/\/vwo.com\/glossary\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Client-Side Testing\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\/\/vwo.com\/glossary\/#website\",\"url\":\"https:\/\/vwo.com\/glossary\/\",\"name\":\"VWO Glossary\",\"description\":\"\",\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\/\/vwo.com\/glossary\/?s={search_term_string}\"},\"query-input\":{\"@type\":\"PropertyValueSpecification\",\"valueRequired\":true,\"valueName\":\"search_term_string\"}}],\"inLanguage\":\"en-US\"},{\"@type\":\"Person\",\"@id\":\"https:\/\/vwo.com\/glossary\/#\/schema\/person\/95c6d9ae0e137e8e23a76689292da18b\",\"name\":\"Aastha Trehan\",\"image\":{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\/\/vwo.com\/glossary\/#\/schema\/person\/image\/\",\"url\":\"https:\/\/secure.gravatar.com\/avatar\/88aead8d5e767617fcf4e13e093c9652c9028cc733abc85e20132b3ca1f5e005?s=96&d=mm&r=g\",\"contentUrl\":\"https:\/\/secure.gravatar.com\/avatar\/88aead8d5e767617fcf4e13e093c9652c9028cc733abc85e20132b3ca1f5e005?s=96&d=mm&r=g\",\"caption\":\"Aastha Trehan\"},\"description\":\"Hi there, I\u2019m Aastha Trehan, Associate Manager of Content at VWO. 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