Five Tips to Analyze Client-Side Performance

As technology is advancing, customers expect mobile applications to provide the required functionalities and a seamless user experience, within the desired response time. Most developers tend to focus their efforts on server-side rendering of the app to bring down the TTFB (time to the first byte), to make the app work fast. However, concentrating the efforts solely on the server-side may not optimize the front-end usability of the app. To make your end-users stay with your organization, you need to deploy client-side tests in your app testing process.

Client-side performance testing metrics allow you to look beyond the server behavior. It helps you to get answers about the end-user experience and improve CX by assessing the app performance from a user’s standpoint. You must not confuse client-side performance directly with RUM (real-user monitoring) performance that the APM tools provide. Some of the basic metrics which you must include in your client-side performance tests are speed index and time to interactive. Speed Index refers to the average time the app takes to display its visible parts on various device combinations. Time to interactive refers to the page interactivity by the network and JS activity. It helps to check the response time of an app from a single user’s viewpoint. 

Client-side tests are end-to-end tests and are not detached from server-side tests. It instead takes a cue from configuring and optimizing the application server to improve the front-end rendering of the app.  Here are some important things you should know about client-side performance testing.

Essential Considerations

The client-side code is written in JavaScript (JS). You can consolidate all your JS files into a single file. The user’s browser will have to download a single file in this case. You can run your JS code with “minimizer” or “minified” to remove comments, extra spaces, and unnecessary elements that are not needed on client-side programs. Reducing the JS size that is sent to the user’s browsers by effectively combining and compressing the files helps to keep the JavaScript execution time in check. JS code minification, compression, removal of unused JS code removing, and JS code caching are valuable steps to reduce the JS execution time. It helps to decrease the page load, providing users with a seamless navigation journey across your app.

Download Time

After the JS is in the user’s browser, the QA needs to gauge how long it takes the JS, CSS, and static contents to download. Once it downloads, the QA should assess the time gap when the requests the page and the content appearing on it. It will enable them to rid of all unused resources, compress images and JS code, and efficiently order the resources to load for removing any possible bottlenecks in your app. 

Client-Side Performance Metrics

  • Page Load Time refers to the time taken between the page to load and start to become interactive. 
  • Page Weight also referred to as “total requests” helps to set weight budgets on a site and is measured in kilobytes or megabytes, and HTML of the page. 
  • Speed Index assigns a score for the page’s visual completeness to determine how long does it take to become visible to the end-users.
  • Time to First Byte indicates the responsiveness of a web server or other network resource.

How To Optimize Client Performance?

While viewing your page, analyze the assets your app serves. You can optimize the large assets, and you can replace or resize large images to the exact image size necessary for the target screen size. Leverage maximum amount of image compression and optimum image formats. Identify large blocking resources, and ensure that there are no duplicate asset downloads. Various scenarios do not require JS support like user preference, script errors, and network/loading errors, and more. Disable JS to evaluate the performance of your app. Also, you should bundle the multiple JS/CSS files, and minify the CSS/JS scripts for a lower load on the network. However, provide the minimum functionality for your app to work without JS. Analyze your app’s DOM node count, as large DOM can lead to greater memory usage, and create costly layout reflows. Use the browser hints such as prefetch, prerender, pre-resolve (DNS), preload, subresource for improving the app’s performance and providing a faster user experience. Based on the application scope, you need to leverage the browser hints. You need to focus on the output that your app serves to your end-users while performing client-side performance testing. 

Execute The Tests

You must execute the client-side performance tests before or during the user application testing (UAT) phase. However, you can also run it after the app or even a single page is ready. Based on your scope, and app testing plan, you need to choose the right testing tool that allows you to conduct the tests as per the chosen metrics. Conduct the tests in an optimized testing environment, and assess the test results to validate the client-side rendering of the app.

To Conclude:

These are some important fundamentals aspects of client-side performance testing. It will enable you to reduce the size and time of JS and CSS downloads, and efficiently improve the quality of the end-user experience.

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