WebPageTest Instant Test

Catchpoint’s WebPageTest Instant test is based on our popular WebPageTest.org platform, and enables you to perform the same types of tests instantly from within the Catchpoint Portal. The WebPageTest Instant Test has most of the same configuration options as the website, so if you have used that platform, it should look pretty familiar. This guide will walk you through submitting a test and interpreting the results.

The daily allotment of free Instant Tests does not apply to Web Page Instant Tests. All Web Page Instant Tests will consume points.

Running an Instant Web Page Test

Follow these steps to run a basic performance test using default settings.

Log into the Catchpoint Portal
In the main menu on the left, select Instant Tests
In the menu bar at the top of the Instant Tests screen, select Web Page (note that you may need to contact Catchpoint Support to have this option added in your portal.)
Click New Test
Input the URL of the web page you want to test in the Enter Website URL field
Select the Location (test node) to run the test from
- Either input the name of the location in the Location field
  -or-
- Click List, then locate and select the desired location
In the Device field, select the desktop browser or mobile device type that you want to run the test.
Click Run Test to execute the test. The results will be available once the test completes, which may take several minutes depending on the website you are testing and the settings selected.

Web Page Instant Test Options

When running an instant Web Page test, there are many options available. This section explains what each option does.

Test Parameters

Connection – specifies the type and speed of internet connection you want the test to emulate.
Browser Dimension – when testing using a Desktop browser, this setting lets you specify the dimensions of the browser window used to test the web page.
Number of Runs – the number of test runs to execute for this Instant Test. By executing multiple test runs, you will get a wider sampling of webpage performance.
Repeat View – causes the page to be loaded twice during each test run.
Tests Performed – choose Site Performance, Lighthouse, or both.
- Site Performance - captures detailed site performance metrics including Core Web Vitals.
- Lighthouse - Google's open-source initiative for auditing the performance of any web page.
Label – you can assign one or more labels to the test, which makes it easier to find specific test results later.

Advanced

Test Duration
- Min test Duration – specifies how long the test will take at minimum. This way, even if the initial page load has completed, the test will continue to watch for any additional activity up to the minimum duration.
- Stop Test at Document Complete – when selected, the test will terminate at Document Complete, regardless of the minimum duration setting.
Capture Settings
- Capture Full Size Video - when enabled, test results will include a full-size video of the browser rendering the webpage.
- Capture Network Packet Trace (tcpdump) - when enabled, test results will include a tcpdump.
- Save Response Bodies for Text Resources- when enabled, response bodies will be displayed under Request Details in Waterfall.
User Agent String
- Preserve Original UA String – save a copy of the original user agent string, which provides information to the website about the connecting device and browser
- Append to UA String – specify additional text to append to the user agent string
- Custom String - specify a fully customized user agent string
Image Support
- Disable AVIF image support - do not load AVIF formatted images
- Disable WEBP image support - do not load WEBP formatted images
Other Settings
- Ignore SSL Certificate Errors - when loading the webpage, disregard any SSL certificate errors
Custom Headers - include a custom header with all requests generated by the browser during the test
Inject Script - include a custom javascript which will run after the page loads

Chromium

Chromium Test Parameters
- Run Carbon Control- when selected, your website's carbon footprint will measured.
- Use Chrome dev tools traffic shaping - can be used to emulate different internet connection characteristics. We recommend using the settings available in the Advanced tab.
- Host Resolver Rules - one or more hostnames and the IP address(es) you want them to resolve to. Settings here will bypass DNS lookup for the specified hosts.
- Command Line - additional Chromium command line switch(es) to customize test behavior.
Capture Settings
- Capture Dev Tools Timeline - when enabled, test results will include the Chrome DevTools timeline trace.
- Capture Network Log - when enabled, test results will include a HAR file listing all network requests.
Trace Settings
- Capture Chrome Trace - when enabled, test results will include Chrome Trace.
  - Trace Categories - a listing of the trace categories to include in the Trace.
- Enable V8 Sampling Profiler - when enabled, the log file will include a sampling of javascript activity that occurred during the test. This results in much larger trace files.
- Capture V8 Runtime Call Stats - when enabled, test results will include certain low-level V8 metrics which aren’t currently exposed in DevTools.

Script

• Script - Enable/Disable including a test script
• Script includes sensitive data - select this option to omit the script from test results
• Discard All HTTP Headers - select to remove all HTTP headers from test results

Block

• Block Requests Containing URL Substrings - specify a list of substrings and the test will block requests containing any of them
• Block Domains Full Host Name - specify a list of host names and the test will block requests to any specified hosts

SPOF (Single Point of Failure)

• Hosts to fail - use this setting to simulate failure of specified domains. All requests for the domains will be rerouted to blackhole.webpagetest.org which will silently drop all requests. Add one host per line.

Custom

Custom Metrics - an arbitrary javascript which will be run at the end of the test to collect custom metrics. Learn More.

Interpreting the Results

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: