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VWO Testing - Server Side

Test and launch complex features with ease and speed

VWO FullStack gives you the server-side flexibility to run omnichannel experiments with deep segmentation capabilities without any performance impact to build consistent, higher-performing experiences.

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Launch experiments from any platform

Built for development teams. View docs

Experiment with everything you build. Deliver better experiences.

Experiment throughout the product stack to discover revenue opportunities while building world-class experiences.

Run versatile A/B tests from the server-side

Run versatile AB tests from the server-side

Test latest features with precision

Test latest features with precision

Feature Flags for effortless rollouts

Rollout - Rollback features with flags

Go beyond testing simple design elements without performance issues

Go beyond testing simple design elements without performance issues

Omnichannel deployment - Curated experiences for all platforms

Omnichannel deployment - Curated experiences for all platforms

Experiment and improve digital experiences across your product


For Marketing Teams

  • Test for higher conversions by serving widely different experiences on any platform.
  • Put your market research to test and target experiences to specific segments.
  • Serve different pricing combos to different customer segments.

For Product Teams

  • Run tests and launch features by running omnichannel experiments without impacting performance.
  • Experiment throughout the product stack to discover revenue opportunities.
  • Decouple deployment from release and assess the impact of new features with phased rollout enabled by flags.
  • Intuitive reports for every distinct environment and mutually exclusive groups.
Engineering Teams

For Engineering Teams

  • Easy to integrate VWO SDKs and get started in 15 mins.
  • Minimum impact on performance.
  • Open source SDKs ensure that user data is never pushed in VWO servers.
  • Easily integrate data end-points with popular tools of Data Warehousing, BI-Analytics, CDP.

Run complex experiments and feature changes

With VWO FullStack, you can literally test anything, be it subscription flows, search algorithms, or any idea that can move your north star metric. Leverage our rich feature set with multi-platform testing, mutually exclusive testing, goal tracking, targeting, scheduling, and more, to optimize product experiences.

Run Complex Experiments and Feature changes

Leverage our advanced reporting and segmentation

Slice and dice test results to discover hidden winners and measure their impact across the funnel. Find out if a specific visitor segment converted drastically different than the others for a specific goal or variation, and use the learnings to optimize features on the go.

Leverage Our Advanced Reporting and Segmentation

Confidently rollout features with minimal risk

Mitigate risk by safely delivering a new feature to a small group of targeted audience before making it live. This enables the product team to control the feature rollout and measure the impact on users, while the development team can seamlessly deliver the feature and monitor the effect on the backend.

Confidently rollout features with minimal risk

No impact on performance. Say goodbye to flickering.

We understand the impact of every microsecond, and with VWO FullStack's server-side testing, the flickering effect is eliminated. With pre-determined experiment variations that are not served on the fly through the browser, the experiment is unnoticeable to the website visitor and has minimal impact on page load time.

illustration to show zero impact on performance and hence no flickering

Advantages of server-side testing with VWO

A/B Testing

Run complex experiments rendered directly from your server and premeditatedly send variations to a visitor's device.

Feature Flags

Decouple deployment from release by creating flags, managing them at runtime, and choosing which user gets to see which feature.

Feature Rollouts

Mitigate risk by safely releasing new features to a small audience before going live.

Feature Testing

Test different feature configurations to determine the variant which delivers the best experience.

Cross-Channel Experimentation

Set your own user IDs to create consistent personalized experiences across all your customer channels for that user ID.

Traffic Allocation

Split traffic between multiple versions of your website and choose the percentage of visitors to be included in your experiment.

Report Segmentation

Slice and dice your test results to uncover hidden winners. Understand how differently visitor segments convert.

User Whitelisting

Quickly assure quality of experiments by driving specific users or user segments into particular variations.


Our SDKs are open source and ensure that user data is never pushed in VWO servers.


Easily integrate the VWO SDKs and get started in 15 mins with minimum performance impact.

Mutually Exclusive

Run multiple experiments on your home page or in-app while ensuring that visitors remain part of a single variation. The data collected for one test will never be affected by any other test.


Get notified whenever there is a change in campaign settings with Webhooks, and receive change event notifications.

Variation Stickiness

Ensure visitors remain bucketed in their respective variations and maintain experience continuity.


Creating individual projects lets you manage and track multiple business experiments simultaneously.


Manage campaigns across development, testing and production environments.


Increase accuracy by creating custom segments to target a specific audience and reduce repetition by saving that segment for later use.

Bayesian SmartStats Engine

SmartStats, our Bayesian statistics engine, is engineered to compute accurate results for all your goals. It is configured to help you make the right business decisions without worrying too much about the statistics. We got you covered there while you focus on important business goals.

Intuitive Reporting

SmartStats is as sophisticated and as easy as you want it to be. While giving you easy-to-digest recommendations and metrics; our advanced reporting mechanism can help you slice and dice to understand each and every aspect of our recommendations.

Frequently Asked Questions

Server-side testing is a method of A/B testing wherein the variations of a particular test are rendered directly from the web server & then deliberately sent to the visitors’ device.

Client-side testing is used when an optimization test involves delivering variations of a webpage that rest on the visitors’ browser. Server-side testing allows tests to be run and modifications to be made directly on the web server & then render the same to the visitor’s browser or mobile app.

An eCommerce store owner, with an aim to optimize for better conversions, wants to test two different checkout flows on both his/her website & mobile app at the same time. As this is not possible by running a simple A/B experiment on the client-side, Server side optimization is required. This type of optimization is more robust and is built for fairly complex tests.

Server-side A/B testing requires a one-time VWO SDK installation, which is integrated into your server application. Whenever a visitor lands on the client browser, a call is sent to the backend server, where the SDK of the server-side testing tool is installed. These settings are then used to create a client instance of SDK, which offers various capabilities like A/B testing by providing a variation to a particular user.

Take Better Business Decisions With Experimentation

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