When an Instant Test is complete the results will be displayed, broken down into the tabs listed.
Summary Tab
The results of a WebPageTest Instant Test run begin in the summary tab. First you will see the URL that was tested, as well as basic configuration settings including the device/browser, internet connection type, node (location), time of the test, and any Labels that were applied to the test. You can add labels to the test here as well. These items are listed at the top of all subsequent tabs as well.
To the right of the summary information is a screenshot of the tested page.
Below the summary information you will see three performance summary cards answering these questions:
- Is it Quick?
- Is it Usable?
- Is it Resilient?=
Page Performance
Key Metrics
- Time to First Byte
The First Byte time is the time from when the user started navigating to the page until the first bit of the server response arrived. The bulk of this time is usually referred to the "back-end time" and is the amount of time the server spent building the page for the user. - Start Render
The Start Render time is the first point in time that something was displayed to the screen. Before this point in time the user was staring at a blank page. This does not necessarily mean the user saw the page content, it could just be something as simple as a background color but it is the first indication of something happening for the user. - First Contentful Paint
How soon did text and images start to appear? - Largest Contentful Paint
When did the largest piece of content in the viewport finish loading? - Speed Index
The Speed Index is the average time at which visible parts of the page are displayed. It is expressed in milliseconds and dependent on size of the view port. - Total Blocking Time
The total amount of time that any request was blocked during the page-loading process. - Cumulative Layout Shift
How much did the layout within the viewport shift while the page was loading? - Page Weight
This is the amount of data that the browser had to download in order to load the page. It is also commonly referred to as "Page Size".
Filmstrip
The filmstrip consists of a series of screenshots taken throughout the page-load process, letting you see exactly how and when different components of the page were loaded.
Real-World Usage Metrics
This section displays Chrome User Experience Report (CrUX) metrics from a sampling of real user sessions on the website captured anonymously, enabling you to compare the performance of this test with the average performance seen by other users.
Lighthouse Scores
Composite performance metrics that provide a summary of webpage performance.
- Performance
Determined by a weighted average of various metrics, each reflecting different aspects of web application page load speed and responsiveness. Google assigns weights to these metrics, and the final score is a number between 0 and 100, with higher scores indicating better performance - Accessibility
A weighted average of multiple accessiblity factors, including whether aria attibutes match their roles, whether buttons have accessible names, etc. - Best Practices
Similar to Accessiblity, a weighted average of many web design factors. - SEO
A measure of search engine optimization based on numerous pass/fail web design factors. - PWA
Evaluates a website’s potential in terms of being a progressive web app, that is how closely the user experience it provides emulates a platform-specific app.
Filmstrip Tab
The filmstrip tab provides a visual keyframe view of the page as it loaded. It also serves as a run comparison tool for multiple test-run filmstrips.
Waterfall Tab
The Waterfall tab provides a Gantt chart breaking down the performance of each individual request generated throughout the page load process, so that you can see how each request impacted page performance.
Lighthouse Tab
The Lighthouse tab summarizes the page's Lighthouse scores, as well as listing results of all audits. You can use the
Opportunities Tab
The Opportunities tab lists opportunities to improve webpage performance as discovered by the Lighthouse audits. Where available, relevant Experiments will be recommended so that you can try out a change to improve performance.
You can enable one or more experiments and click Run Experiments to rerun the test with each selected experiment enabled.
Experiments Tab
The Experiments tab lists recommended experiments that may improve web page performance.
Each recommended experiment includes an explanation and any configuration options required to run the experiment. You can run one or more experiments by selecting "Run this Experiment", completing any configuration fields, and clicking Run Experiments at the bottom.
Assets Tab
The Assets tab provides details about the individual files loaded during the test, as well as optimization options for each file.
Optimization Summary
This section grades the performance of the assets on the page by a range of key metrics and performance indicators.
Breakdown by MIME Type
This section shows a breakdown of assets in the page by MIME type, and shows for each type how many requests there were, the number of bytes, and the number of bytes when uncompressed.
Optimization Checklist
This section shows a list of requests and potential optimizations for each one, so that you know which have been complete and which you might still implement.
Optimization Details
This section goes through every optimization type and shows you exactly what request results resulted in each recommendation.
Javascript Tab
This javascript tab provides a detailed breakdown of javascript activity on the page, including a breakdown of processing categories, specific processing events, and a complete console log.
Comparing Test Results
You can easily compare the results of multiple instant tests in one screen to see how the tests performed side-by-side. Simply go to the Instant Tests screen, select two to four instant tests from the Test History, and click Compare Tests.
The comparison screen will show you the results from the selected tests side-by-side:
