Configure Core Web Vitals

NeoLoad allows you to enable Core Web Vitals monitoring for your performance tests to capture essential metrics that provide insights into user experience.

You can configure Core Web Vitals using two methods: through the post-recording wizard or by adding actions during user path design. Both approaches give you the flexibility to add user experience monitoring to new and existing test scenarios.

Before you start

Core Web Vitals works with RealBrowser user paths to capture client-side performance metrics.

Before you configure Core Web Vitals, make sure you have a NeoLoad project. You can start with an empty project or use existing RealBrowser user paths.

Configuration methods

Understanding the different configuration approaches helps you choose the best method for your testing needs.

You can configure Core Web Vitals monitoring using these methods:

The post-recording wizard offers the simplest way to enable Core Web Vitals monitoring.

When you enable Core Web Vitals through the post-recording wizard, the captureWebVitals action is automatically added at the beginning of your RealBrowser user path. This provides a simple way to enable monitoring for the entire user path without manual configuration.

Manual configuration gives you precise control over where Core Web Vitals metrics are captured in your user path. The best practice is to add captureWebVitals at the beginning of the User Path before the first navigation to make sure you collect all the metrics.

For more control over where Core Web Vitals are captured, you can add captureWebVitals actions manually using either:

  • Contextual menu: Right-click at the desired location in your user path and select Add captureWebVitals action from the advanced contextual menu.

  • Drag and drop: Drag the captureWebVitals action from the action menu and drop it at the desired location in your user path.

Enable Core Web Vitals after recording

The post-recording wizard provides the quickest way to enable Core Web Vitals for completed recordings.

To enable Core Web Vitals after recording for existing user paths, follow these steps:

  1. Open your recorded user path in the NeoLoad design interface.

  2. Go to Recording > Post Recording Wizard .

  3. In the wizard, locate the Core Web Vitals section.

  4. Select Enable Web Vitals to activate monitoring for this user path.

  5. Select Apply to save your configuration.

The wizard will automatically add the captureWebVitals action at the beginning of your user path.

Enable Core Web Vitals during user path design

This method allows you to add Core Web Vitals monitoring with precise control over placement.

You can add Core Web Vitals monitoring to user paths outside of the recording process. To enable Core Web Vitals during user path design, follow these steps:

  1. Open your user path in the NeoLoad design interface.

  2. Right-click at the location where you want to add monitoring to open the advanced contextual menu.

  3. Select Add captureWebVitals action from the menu options.

  4. The action is added to your user path.

  5. Configure the captureWebVitals action parameters as needed. By default, the action has no parameters and will capture Core Web Vitals for subsequent page loads.

The captureWebVitals action will monitor all three core metrics (LCP, INP, and CLS) for any page the user visits after the action is added.

Ensure measurement accuracy

NeoLoad captures multiple measurements for each Core Web Vitals metric on a single page and reports only the final measurement. This approach provides the most accurate representation of user experience.

Note: If your user path navigates away from the current page before the final Core Web Vitals measurement completes, NeoLoad reports an incomplete value that may be lower than the actual user experience.

CLS (Cumulative Layout Shift) measurements require special attention because page content can shift after navigation appears complete.

Consider this scenario: your user path waits 3 seconds before moving to the next step. If the final CLS measurement occurs within those 3 seconds, the reported value accurately reflects user experience. However, under high load conditions, the system under test responds more slowly, and the user path may advance before capturing the final CLS measurement.

This timing issue results in inaccurately low CLS values that don't represent true user experience.

Configure your user paths with adequate wait times to ensure complete metric capture.

To prevent incomplete measurements:

  • Increase wait times before navigating away from pages, especially for high-load test scenarios.

  • Account for slower system response times when the system under test experiences increased load.

  • Test your user path timing under various load conditions to verify measurement completeness.

  • Prevent the Load Generators to have its CPU over-saturated (>90%) at all times.

What's next?

Now that you've configured Core Web Vitals monitoring, analyze your Core Web Vitals results to gain insights into your application's user experience performance. Also, to learn more about how to effectively capture Core Web Vitals with Tricentis NeoLoad RealBrowser, check out our Tricentis Academy course.