The Talent500 Blog
Things to keep in mind during front end performance testing 1

Things to keep in mind during front end performance testing

Developers need to perform several performance tests before launching a website or application. The back end and front end performance tests are mandatory to ensure that the application works properly and meets users’ expectations.

Front end performance testing helps you determine whether the built application is made as instructed by the developers or not. It tests browser-based applications or services for load speed, user interface design, responsiveness, and functionalities.

What is front end performance testing?

A front end performance test is a user-oriented test to check the usability of a program or a webpage. It verifies the presentation architecture of the system from the user’s point of view to ensure the functionality of various function buttons, tabs, and other display elements.

For instance, the performance testing of a school website will include inspecting all display elements and checking if they are in place and easy to navigate. Also, the front end performance test will affirm that other essential features such as access to the school curriculum, form downloads, and e-learning portal are operational.

Comprehensive front-end performance testing is essential to deploy robust and usable applications and websites. Without a doubt, front end performance testing can be challenging. This article will explore these challenges and discuss ways to meet them.

1. Understanding the elements of front-end performance 

You can’t fix the issue if you are unaware of its occurrence. Front-end testing tools like Google PageSpeedLighthouse, and GTmetrix provide an instant glimpse of essential front-end elements that QA testers must know.

Important metrics to know:

First Contentful Paint (FCP): According to Mozilla“First Contentful Paint (FCP) is when the browser renders the first bit of content from the DOM, providing the first feedback to the user that the page is actually loading.” FCP is important to consider as it tells how fast the first text, image, and non-white canvas content is rendered when a user opens the URL. It is the first time when users have started consuming the page content.

First Input Delay (FID): It measures the time lapse between when a user first interacts with the web page, such as clicking a button, filling in a form, or any custom JavaScript-powered control, and when the browser can respond to the interaction.

Render-blocking resources: These are the resources that block or delay the browser from rendering the page content on screen, thereby increasing the load time. It can include stylesheets, scripts, and HTML imports. It is essential to eliminate render-blocking of resources to load the page faster.

Switch to HTTP2: Modern servers support a new version of HTTP Protocol, allowing web browsers to utilize multithreaded and multicore capabilities to make apps and web pages function faster. Using HTTP2 Protocol offers many improvements:

  • It can accept multiple simultaneous requests on the same connection.
  • There is no need to negotiate and re-create a link for each request, saving lost time.
  • It can send multiple files into one response (multiplexing).
  • It offers better compression (30% higher).

2. Testing in proxy and legacy browsers

While Chrome and Firefox have over 67% of the market share, there are other browsers too. You must test for proxy and legacy browsers as well. Browser use varies from country to country. For instance, UC Browser and Opera Mini have a significant market share in Asia.

Front end performance optimization tools like BrowserStack can help you create custom test cases depending on average internet speed in a market, network throttling, and type of device.

3. Testing 404 pages

Don’t skip testing 404 pages. In a research, Matt Hobbs discovered that the 404 responses clients receive could be huge. He found that most 404 reactions result from missing images, favicons, broken JS requests, CSS and font files, and more.

Testing and optimizing 404 pages is necessary. Include a small error payload in these pages to improve server response time.

4. Using Performance Diagnostic CSS

You can use CSS to identify some of the performance issues quickly. Tim Kadlec created the idea of Performance Diagnostic CSS, which is further inspired by Harry Robert’s code snippet.

If you visit the link above, you will see how brilliantly Roberts used CSS to highlight common issues like legacy format images, unsized images, and synchronous scripts.

Performance Diagnostic CSS can be an excellent front end testing tool to detect errors and issues that can cause performance issues visually.

5. RUM-solutions to monitor changes in performance over time

It is impossible to control your users’ digital experience and their level of satisfaction without a monitoring strategy. Real User Monitoring (RUM) tools can help visualize how users interact with your app or website from their perspective. You can automate continuous monitoring with front end testing tools like CalibreSpeedCurve, and Site speed. These tools allow measuring business-specific metrics for performance enhancement. You can set your user-timing marks and automatic alerts to monitor performance changes over time for comprehensive testing.


Front end performance testing helps paint a complete picture of how your website or web app will perform in the real world. Factor in the insights we shared above to cover all the aspects prone to performance anomalies and get actionable insights faster.

Talent500 is the platform that lets you work from anywhere for the world’s best companies. Join our community and connect with global businesses.


Manik Sharma

Manik Sharma specializes primarily in UI or Software Development using Javascript libraries like React and Redux along with HTML, CSS, and other libraries like Bootstrap, Node.js, Express.js, MongoDB. He loves to talk business and think of cool startup ideas. Definitely, an entrepreneur in making. He is equally interested in discussing innovative ideas that can make a huge difference in someone's life.

Add comment