(Image is generated by Midjourney)
Introduction
Web performance is a critical factor that affects the success of any website. Users expect fast and responsive websites; if a site is slow to load, it can lead to high bounce rates and low engagement. Therefore, it is essential to measure and optimize web performance regularly.
Web performance optimization (WPO) is the process of improving the speed and efficiency of websites. It's important because it can have a significant impact on your bottom line, including:
Increased revenue
Decreased costs
Better user experience
Important Performance Metrics
To measure web performance, several metrics have been developed to help web developers and businesses assess the speed and responsiveness of their websites. These metrics are used to evaluate different aspects of a website's performance, including its loading speed, interactivity, and visual stability. In this blog post, we'll take a look at some of the most important web performance metrics, including FCP, LPC, TTI, and DCL.
FCP (First Contentful Paint)
FCP is a web performance metric that measures the time it takes for the first piece of content to appear on a user's screen after they have clicked on a link or entered a URL. This content could be an image, text, or any other element that is visible to the user. FCP is important because it gives users an indication that the page is loading and helps them understand how long they may need to wait before they can start using the website. A good FCP score is under 1.5 seconds.
LPC (Largest Contentful Paint)
LPC is a web performance metric that measures the time it takes for the largest element on a web page to become visible to the user. The largest element could be an image, a video, or any other visible element on the page. LPC is important because it gives users an idea of how long they may need to wait before they can start using the main content of the page. A good LPC score is under 2.5 seconds.
TTI (Time to Interactive)
TTI is a web performance metric that measures the time it takes for a web page to become interactive. In other words, TTI measures the time it takes for a user to be able to interact with the elements on a web page, such as clicking on links, scrolling, and filling out forms. A good TTI score is under 5 seconds.
Total Blocking Time (TBT)
It measures the total amount of time between FCP and TTI where the main thread was blocked for long enough to prevent input responsiveness. A good TBT time is under 200 milliseconds.
Cumulative Layout Shift (CLS)
It measures the cumulative score of all unexpected layout shifts that occur between when the page starts loading and when its lifecycle state changes to hidden. A good CLS score is 0.1 or less
DCL (DomContentLoaded)
DCL is a web performance metric that measures the time it takes for a web page to load its HTML, CSS, and JavaScript files. DCL is important because it gives users an idea of how long they may need to wait before they can start using the website. A good DCL score is under 2 seconds.
How metrics are measured
Performance metrics are generally measured in one of two ways:
In the lab: using tools to simulate a page load in a consistent, controlled environment
In the field: on real users loading and interacting with the page
In the lab
Testing performance in the lab is essential when developing new features. Before features are released in production, it's impossible to measure their performance characteristics on real users, so testing them in the lab before the feature is released is the best way to prevent performance regressions.
In the field
On the other hand, while testing in the lab is a reasonable proxy for performance, it isn't necessarily reflective of how all users experience your site in the wild.
The performance of a site can vary dramatically based on a user's device capabilities and network conditions. It can also vary based on whether (or how) a user is interacting with the page.
Moreover, page loads may not be deterministic. For example, sites that load personalized content or ads may experience vastly different performance characteristics from user to user. A lab test will not capture those differences.
The only way to truly know how your site performs for your users is to measure its performance as those users are loading and interacting with it. This type of measurement is commonly referred to as Real User Monitoring—or RUM for short.
Measuring Performance
To measure the performance of a website, you can use a web performance tool. There are many different tools available, but we'll be focusing on Google PageSpeed Insights and Chrome DevTools because they're free and easy to use.
Google PageSpeed Insights: https://developers.google.com/speed/pagespeed/insights/#mobile
Chrome DevTools:
https://developer.chrome.com/devtools
Way to Optimize Websites
Optimizing Images
Optimizing images is one of the most important steps in improving website performance. Images can make up a large portion of your site's total size, so it's important to keep them as small and efficient as possible.
There are several ways you can optimize your images:
Resize and compress - When you resize an image, you're reducing its dimensions while maintaining its aspect ratio (the relationship between height and width). Compressing an image reduces its file size by removing unnecessary data without losing quality or detail.
Use vector graphics - Vector graphics are made up of lines instead of pixels like rasterized (pixelated) images do. This means that vector graphics don't lose quality when resized because they don't contain any pixel information--they only have line information that scales smoothly at any resolution without losing sharpness or clarity.* Use the right file type - Different types of files require different amounts of processing power from computers when viewed online; some formats also require different amounts from mobile devices than others do! It's best practice to use PNGs over JPEGs whenever possible because they compress better than JPEGs do without sacrificing much quality at all."
Optimizing Code
Optimizing code is one of the most effective ways to improve your website's performance. The first step is to minimize and concatenate HTML, CSS, and JavaScript files. You can do this using tools like Gulp or Webpack, or by manually editing your code with an editor like Sublime Text.
Next, consider using a Content Delivery Network (CDN) for images and other static assets so they load faster from servers closer to users around the world. Finally, caching allows you to store content on your server so it doesn't need to be regenerated every time someone visits your site
Optimizing Server Response Time
Optimizing Server Response Time
Enabling compression
Using a content delivery network (CDN)
Optimizing database queries
Using a lightweight web server
Optimizing Web Fonts
You can optimize web fonts by using them sparingly, making sure to use the right font formats, and using the new font-display property.
Fonts are a big part of what makes a website look good, but they can also be a big drain on performance. For example, if you have 10 words on your page and they're all in different fonts (a common practice), those 10 words will load 10 separate times before being displayed on screen--and each time one loads it has to go through all of its own HTTP requests for things like images and JavaScript files as well! This means that even though there may only be two or three different types of fonts being used throughout your site's design process (e.g., Helvetica Neue Light for headings; Roboto Regular for body copy), each instance will still need its own separate HTTP request just like any other asset would require one too--which adds up quickly when you consider how many times we scroll through pages every day while browsing online content!
Optimizing Third-Party Scripts
When it comes to third-party scripts, you should be aware of the following:
Choosing the right third-party scripts: You should only use scripts that are necessary for your website's functionality or user experience. If you don't need a particular script, don't include it in your site!
Loading scripts asynchronously: Loading JavaScript files asynchronously is one of the best ways to improve page load times because it allows them to load in parallel with other resources on your page. This means that they won't block rendering and cause delays in loading other resources like images or CSS stylesheets (which can happen if they're loaded synchronously).
Using pre-connect and preload: These two new browser standards allow websites to specify their intention to connect with another server before making an actual request over HTTP/2 (or HTTPS). This way if there's any delay between when those connections are made and when actual requests start coming through again later downstream during page load periods then they'll still be ready waiting patiently there ready to go without having any impact whatsoever on performance metrics such as TTFB measurements which measure how long things take from start until finish including delays etc., so keep this tip handy next time someone asks why aren't we seeing better results yet?
Some other Performance Matrics
Perceived load speed: how quickly a page can load and render all of its visual elements to the screen.
Load responsiveness: how quickly a page can load and execute any required JavaScript code for components to respond quickly to user interaction
Runtime responsiveness: after the page load, how quickly can the page respond to user interaction.
Visual stability: do elements on the page shift in ways that users don't expect and potentially interfere with their interactions?
Smoothness: do transitions and animations render at a consistent frame rate and flow fluidly from one state to the next?
Given all the above types of performance metrics, it's hopefully clear that no single metric is sufficient to capture all the performance characteristics of a page.
Conclusion
In conclusion, measuring web performance is crucial for ensuring that users have a positive experience on a website. FCP, LPC, TTI, and DCL are some of the most important web performance metrics that web developers and businesses should track regularly. By optimizing these metrics, businesses can ensure that their websites are fast and responsive, leading to higher engagement and better user satisfaction.