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What Is a Website Performance Test?

A website performance test evaluates how a website performs and behaves in different situations and under various conditions. Website performance testing is designed to ensure that sites are accessible and responsive, and that they provide an optimal user experience on different devices and with various network conditions. The objective of a website performance test is to pinpoint and fix any bottlenecks or issues with performance that might slow websites down, impact user satisfaction, or damage customer relationships and business outcomes.

The need for website performance tests

A website is a mission-critical part of business today. By engaging customers and prospects online, websites promote brand identity, build brand awareness, drive sales, enhance business reputation, and strengthen customer loyalty. A poorly performing website jeopardizes each of these objectives.

Customers and business users expect websites to be available, fast, and easy to use. When sites fail to meet these expectations, the online experience is subpar, and users will quickly go elsewhere. A website performance test helps to avoid this by quickly uncovering issues so that web administrators can solve them before they impact user experiences.

Benefits of testing

Organizations can use website performance test results to:

  • Improve the user experience (UX). The ultimate goal of a website performance test is to ensure better online experiences for users. By improving website loading speed, eliminating bottlenecks, promoting scalability, avoiding downtime, and ensuring functionality, website performance testing helps to meet and exceed users expectations.
  • Improve mobile experiences. Users increasingly access websites on mobile devices like smartphones and tablets. A web performance test can help to make sure that sites are optimized for these mobile experiences.
  • Enhance brand perception. When customers have easy and pleasurable experiences on a website, their perception of the company’s brand increases. Conversely, when websites don’t work well, brand perception plummets.
  • Increase conversion rates. Websites that perform well will engage users more effectively, keep them on sites longer, and lead them to actions that build better customer relationships and boost sales.
  • Enhance search rankings. High-performing websites are likely to rank higher than sites with problems, no matter how good the site’s content may be.

What tests measure

A web performance test is designed to track site performance as it relates to speed, load times, response times, and scalability. Common site and page performance metrics include:

  • Page load time: The average time it takes an entire page to render in a browser.
  • Time to first byte (TTFB): This tracks latency of a web server and measures the time between a user’s request for a web page and when the server sends back the first bit of information.
  • Start render time: The amount of time it takes for the content of a page to begin displaying after a user requests a website.
  • Page size: The total size of all resources — including HTML, CSS files, images, and JavaScript — that must be downloaded to render a page.
  • Time to title: The time that it takes the title of a website to appear in the browser tab.
  • Time to interactive: The amount of time before a user can begin interacting with a web page.
  • DNS lookup time: The amount of time that the Domain Name System (DNS) takes to convert the domain name entered by a user into the corresponding IP address for a website.
  • Speed index: The amount of time that a website loads its “above-the-fold” content.
  • Bounce rate: The percentage of users who land on a page but leave without clicking anything or interacting with it.
  • Session duration: The length of time a user spends on a page.
  • Conversion rate: The percentage of total visitors that complete a desired action such as making a purchase, downloading gated content, or signing up for a newsletter.
  • Error rate: The percentage of HTTP requests that result in error codes.

Factors affecting website performance

Website performance testing can help to uncover a variety of issues that can degrade a site’s performance and speed.

  • Page weight: This is the total size of a web page and all the resources, like images and code files, required to load. Highly complex pages have a higher page weight and take longer to load.
  • Unoptimized images: Images on a website are much larger than text files and take longer to load and render. Optimizing images by resizing them and compressing them can help to improve load times.
  • Excessive HTTP requests: Browsers request the elements of a web page by sending an HTTP request to the website’s hosting server, which responds with the requested resources. Highly complex pages require multiple HTTP requests and take longer to load.
  • Lack of caching: When web data like HTML files and images are stored in a user’s browser cache, that data can be loaded much more quickly on repeat visits than files sent from a web server.
  • Lack of file compression: The larger the file, the longer it takes to load. File compression can help pages load more quickly.
  • Heavy use of JavaScript/CSS: On some pages, certain code — usually for CSS or JavaScript — loads by default before other page content, even if it’s not required for above-the-fold content that the user sees before other page elements.
  • Server performance: Slow server response times directly impact site speed.

Types of tests

Web developers and web administrators use a variety of website speed tests and performance tests to pinpoint and remediate performance issues.

  • Baseline testing establishes a performance benchmark for future comparisons.
  • Comparative testing compares performance against competitors or previous versions of a site.
  • Stress testing determines the maximum capacity of a website before performance degrades.
  • Load testing evaluates performance under expected traffic conditions.
  • Browser testing tests how the website performs across different web browsers.
  • Soak testing (also called endurance testing) tests a site’s ability to manage a constant load.
  • Spike testing determines whether a website can accommodate a quick and large spike in traffic.
  • Capacity testing determines how many concurrent users a site can accommodate before performance degrades.
  • Scalability testing determines whether a website or application can effectively accommodate loads that consistently increase.
  • Isolation testing is a repeating test to see if a previously detected issue or error has been fixed.

Common website performance test solutions

Web administrators today have a wealth of website performance test solutions to choose from. Providers like Akamai mPulse and CloudTest, Google PageSpeed Insights, GTmetrix, Pingdom, WebPageTest, and Lighthouse combine speed test tools with capabilities for finding JavaScript and CSS issues as well as images that must be optimized, SEO errors, and accessibility issues.

A web performance test tools should offer:

  • Comprehensive capabilities. The best tools combine multiple features to help address various aspects of website performance.
  • Flexibility. Testers should have the option to test from different locations, on a range of devices, and under various conditions.
  • Ease of use. Superior tools are easy to use and understand, even for nontechnical users.
  • Detailed reports. When reports are clear and include suggestions for optimizations, testers can pinpoint issues and remediate problems faster.
  • Integration capabilities. The ability to integrate with other tools or services will allow for comprehensive and continuous monitoring.

Frequently Asked Questions (FAQ)

Website performance monitoring is the task of tracking, evaluating, and testing a website’s performance. Monitoring ensures that sites and web pages are easily available to users, that a site is secure, that pages load quickly, and that functions work as intended.

Real-user monitoring (RUM) and synthetic testing are two approaches to monitoring and testing web performance. RUM monitors the performance of a website from the machines of actual users, tracking their real-time interactions and their real-world experiences on a website. Synthetic testing uses scripts that simulate the interactions and paths that a user might take through a website or application, helping developers test at various points in the lifecycle of a website. Synthetic testing is great for consistent testing and for regression testing as changes are made to sites. RUM provides vital data about how well sites are performing for actual users.

Google Core Web Vitals are three metrics that track speed, interactivity, and visual stability on a web page. Core Web Vitals include:

  • Largest Contentful Paint (LCP), measuring how long it takes for the largest content element on a page to load.
  • Cumulative Layout Shift (CLS), measuring how a page’s layout shifts or changes unexpectedly when loading, which can frustrate users.
  • Interaction to Next Paint (INP), measuring the longest duration of a response from interaction until paint in a page’s lifespan.
  • First Input Delay (FID), measuring how long it takes for a browser to respond to the user’s first click or tap on a page.

Together, these metrics are considered to be the most important factors in improving user experiences and optimizing pages for search engine rankings.

Why customers choose Akamai

Akamai powers and protects life online. Leading companies worldwide choose Akamai to build, deliver, and secure their digital experiences — helping billions of people live, work, and play every day. Akamai Connected Cloud, a massively distributed edge and cloud platform, puts apps and experiences closer to users and keeps threats farther away.

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