How to optimize website performance: Step-by-step guide

There's a clear relation between web performance, user experience, online visibility, and conversions. Users leave online stores that load slowly or jitter, and Google penalizes such websites in search results. According to Forrester Research, the likelihood that a visitor will purchase, sign up, or take other actions on a poorly optimized website is lower by up to 400%.

Even if you do everything else right, your business might suffer from poor web performance. Website optimization must be approached systematically, taking steps to ensure everything from the frontend user experience to backend processes runs without any bottlenecks.

What is website performance optimization?

Definition of website performance

Website performance is the objective measure of a site's speed, responsiveness, and visual stability. It takes into account not just the underlying code and infrastructure, but also different devices and network connectivity capabilities.

Early websites were static HTMLs reached with slow dial-up connections, so file size was the most important metric determining web performance. As websites became more complex, raw speed was supplemented by user experience signals, such as loading times and interactivity.

Why website performance matters

Performance optimization tasks are at the intersection of web development, user experience, and Search Engine Optimization (SEO). Failure to optimize your website has far-reaching business consequences:

• Brand trust. Research shows that websites that load for longer than three seconds are seen as untrustworthy by users. A fast site with a smooth user experience signals reliability even before a single word is read.

• User retention. Well-performing sites reduce bounce rates as visitors are inclined to stay on the site for longer. Low retention signals to search engines that the site is causing frustration to visitors.

• SEO rankings. Better performance means more visibility in search engine rankings. Google has officially signaled for years now that website performance is a ranking factor.

• Conversion rates. Studies consistently show that even a one-second delay in load times can reduce conversions by 7%. Whatever your conversion goals are, a better-performing site will benefit from them.

• Compatibility. Optimizing web performance ensures users can access your site regardless of the device they're using. Mobile traffic is consistently growing year-over-year, making it increasingly important to optimize for all devices.

Key website performance metrics to track

Core Web Vitals

Core Web Vitals are a set of standardized metrics used to measure the real-world performance of websites for ranking them in Google search. The three metrics introduced in 2020 shifted how we think about site performance. Instead of purely technical benchmarks, they capture how users perceive the site's performance.

• Largest Contentful Paint (LCP) measures the loading performance of a page's main content, often the hero image or a headline, for a visitor

• Interaction to Next Paint (INP) measures responsiveness to user interactions, such as clicks, reporting on the near-slowest input throughout a page visit.

• Cumulative Layout Shift (CLS) measures the visual stability by quantifying how much the page elements move around while loading.

Additional performance metrics

Several other supporting metrics can help you diagnose more accurately why your site's performance is slow and where exactly to intervene.

• Page Weight refers to the total size of all the assets of a page.

• Time to First Byte (TTFB) measures how long it takes for the browser to receive the first byte of data from the server.

• First Contentful Paint (FCP) captures the moment the page loads the first DOM element of the page.

• Time to Interactive (TTI) shows how long it takes for the page to become fully interactive. Today, it’s largely deprecated due to how sensitive the metric is to outliers.

• Total Blocking Time (TBT) represents the total time during which the site is unresponsive to user input during loading.

What are good performance scores?

A well-performing website will have a good score across all the metrics we discussed, but a poorly-performing one can have a low score on at least one. The severity of performance issues for a website depends on which metrics are underperforming. 

LCP, INP, and CLS are generally considered the most important ones as they all affect the users the most and are the measures Google uses. The others serve as good diagnostic tools.

Step 1: Measure your website performance

Use website speed testing tools

Optimizing your site's performance without measuring first will leave you guessing what improvements are actually needed. Using Google's PageSpeed Insights is a natural starting point, providing lab and real-world data to work with.

You'll find the core LCP, INP, and CLS metrics we discussed earlier. The data you'll find there will give you a baseline for further improvements. Uxify tools can help you implement ongoing monitoring with more real-world user data.

How to interpret performance reports

Any poor scores for core vitals should be fixed as soon as possible, as they have the most impact on user experience and SEO rankings. While working with the data, it's important to document the relevant scores for both mobile and desktop, and to highlight improvement opportunities.

Further metrics will help you to narrow down the issues and pinpoint what needs to be solved specifically. For example, TTFB can indicate whether the problem originates at the server level or on the frontend.

Establish performance benchmarks

Once you make the initial metrics, they become your initial benchmarks against which every future improvement will need to be measured. Focus on a few of the most important pages, such as your home page, key landings, or crucial product pages, and set page speed scores for mobile and desktop.

The benchmarks should be aligned with good performance scores as a target. Once a website update or other change pushes a metric below the acceptable threshold, you'll need to revisit. Treat the benchmarks and targets as an ongoing project.

Step 2: Optimize hosting and server performance

Choose high-performance hosting

A slow hosting server can undermine all of your optimization efforts, so it's the best place to start. Avoid cheap shared hosting plans and opt for a VPS, cloud, or managed WordPress hosting, depending on your site's scale and niche. The server's location is also important since a server physically close to your audience will perform better.

Use a Content Delivery Network (CDN)

A CDN is a distributed network of servers that stores cached copies of your site's assets, such as images, CSS, and JavaScript files. Without a CDN, every request travels to your original hosting server, which makes the website slower and less resilient to traffic spikes, DDoS attacks, and other issues.

Enable modern web protocols

Newer protocols are more efficient at handling your website's traffic. HTTP/2, for example, allows multiple requests to be handled simultaneously, while the older HTTP/1 requires sequential processing. Additionally, it's worth looking into whether your server reduces the size of HTML, CSS, and JavaScript files before they are transmitted.

Reduce Server Response Time (TTFB)

Time to First Byte (TTFB) directly measures a server's performance. A high TTFB means your server is taking too long to process requests, and everything else is delayed as a consequence. Keeping your database optimized, removing unused plugins, and ensuring your server software is up to date all contribute to keeping TTFB under 800 milliseconds.

Step 3: Optimize frontend performance

Minify CSS, JavaScript, and HTML

Minification is the process of stripping all that is unnecessary from the CSS style sheets, JavaScript, and HTML files. The goal is to reduce the file sizes without changing how the website functions, resulting in a faster web performance. Most modern development tools, including AI-driven speed optimization tools, can help you go through such a process.

Reduce HTTP requests

Every page element triggers a separate HTTP request. The more such requests a browser has to make, the longer a site takes to load. Combining CSS and JavaScript files, removing unused plugins, and auditing your page regularly to free up requests are practical steps to take. It's also important to prioritize critical requests and use lazy loading for non-essential ones.

Eliminate render-blocking resources

Render-blocking resources are one of the most common reasons pages feel slow. They are CSS or JavaScript files that have to be fully processed before loading the rest of the page. The fix involves loading such elements asynchronously or deferring them so it doesn't interrupt rendering of more critical parts of the page content.

Enable file compression

Compressing files before sending them to the visitor's server can dramatically reduce load times. Gzip and Brotli are the two standard compression methods, with Brotli being the more modern one. Enabling either of them on your server will have an immediate impact on how fast the frontend of your website loads.

Step 4: Optimize images and media

Compress images without losing quality

Image compression eliminates parts that human visitors don't notice or cannot distinguish. Most websites use a moderate level of lossy compression to discard some part of the images to increase load times. Reducing the full size without pixel loss (lossless compression) is also used. The main rule with both is not to send an image larger than needed.

Use modern image formats

JPEG and PNG have been web standards for decades, but newer formats like WebP and AVIF can be more lightweight. Browser support for modern image formats is now broad enough to implement them without much worry. However, to avoid incompatibilities, it's often better to serve newer formats only to browsers that support them.

Implement lazy loading

Images can be significantly optimized with lazy loading, where each image loads only when they approach what the user. In practice, this means that the page is loaded faster because resources aren't wasted on content that's never visible to the user. Longer and more image-heavy pages will benefit more from such optimization.

Use responsive images

One of the most common performance optimization mistakes is sending images that are too big for the user's screen. Downloading the larger image still costs performance resources and slows down the website. Responsive images solve this issue by defining multiple sizes and automatically selecting the one that fits the user's device best.

Step 5: Implement effective caching

Browser caching

Caching solves the problem of users downloading the same files repeatedly. Copies of your website's resources can be stored in the user's browser for a defined period. With browser caching, the next visit of a user will have much faster load times, as parts of the website are on the user's device already.

Server-side caching

If browser caching benefits returning visitors, server-side caching improves the performance of everyone else. It stores a pre-built version of the website and can serve it much faster. Server-side caching is particularly impactful for websites relying on databases or CMS platforms, where each request may trigger different servers.

CDN caching

Your Content Delivery Network (CDN) can distribute cached copies of your assets across servers located in different regions. It allows the website to be loaded from the CDN server that is geographically closest, improving the loading performance. Using CDN networks, like Cloudflare or Akamai, is standard for all websites with global traffic.

Configure cache-control headers

Cache-control headers define how long a resource should be cached, whether it's stored in the browser, server, or CDN, and under what conditions it's used. The exact configuration depends on your optimization strategy. Generally, setting long cache durations on static resources while applying shorter ones to website parts that frequently change is effective.

Step 6: Optimize JavaScript performance

Remove unused JavaScript

Unlike images or other media files, JavaScript isn't simply downloaded and displayed, but must be executed. This means that all such scripts drain the resources of the user's machine. JavaScript's impact on slower or mobile devices is especially noticeable, so removing unused scripts is essential for a responsive site.

Defer non-critical JavaScript

By default, most scripts run synchronously, so the browser pauses to render them all before loading the page fully. Deferring non-critical scripts helps the browser to continue rendering select parts of the page and execute others on notice. It's up to your optimization strategy to decide what content is the most important.

Use code splitting

Code splitting organizes your scripts into purpose-specific chunks that are loaded only when the user needs them. Unlike in older JavaScript loading approaches, opening the loading page doesn't require executing all JavaScript related to the site. Most modern bundlers and frameworks support code splitting natively to improve your web performance.

Minimize third-party scripts

If deferring and splitting scripts is not enough, minimizing the use of third-party ones might be the next best option. They are some of the most common and least controllable sources of resource drain. The process requires auditing every third-party script, determining its performance costs, and questioning whether they earn it.

Monitor and maintain website performance

The optimization steps we covered aren't a one-time task. Site performance tends to degrade with every change to the website. New content, plugins, images, or changed traffic patterns might shift the performance of your website.

It's crucial to track Core Web Vitals regularly, as it can show you pages that are degrading before they start affecting search rankings or conversion rates. Having a dedicated time and a person in an organization who checks on it helps to keep the monitoring consistent.

Yet, testing your site only with automated tools like PageSpeed Insights might not be enough. Real User Monitoring (RUM) tools capture performance data from actual daily visits of your users, giving you a closer to real-world picture of your site speed.

By adding real-user monitoring signals and even additional engagement metrics, like early exit rate or time to engage, Uxify connects current data with proactive improvements. Your website data can then be benchmarked against competitors to identify usage patterns and opportunities to tie everything to revenue metrics.

Without bridging such a gap, it's much more difficult to define your maximum acceptable values for key performance metrics. For example, keep LCP under three seconds or total page weight under 2 megabytes. Such a "performance budget" creates accountability and gives you guidelines on when more investments in page performance are needed.

Common website performance mistakes

As with most things in SEO and web development, it's always best to act only when you have enough credible data to justify your decisions. The biggest general mistake is blindly optimizing your website without measuring relevant metrics first.

A few more specific mistakes are also worth noting. They represent common recurring patterns that, if unaddressed, may erode your site's performance over time.

• Large uncompressed images are one of the most common performance burdens to a website's speed. Images not converted into modern formats add unnecessary weight to every page load that the user's device must handle.

• Too many third-party scripts add external dependencies to your server that you often have no control over. Using only the most essential scripts and addons helps to improve load times and reduce potential blocks.

• Slow hosting undermines every other positive action you might take to improve your site's performance. If your hosting server is slow, TTFB and every subsequent metric suffer.

• Excessive redirects introduce latency, and the delays compound over time, slowing down the website. This is more common for sites that have undergone migrations or URL restructuring.

• Large JavaScript bundles block the browser's main thread, inflating INP score. It's best to optimize JavaScript to send only what is needed for the current page or its element to load.

Conclusion

Website performance optimization is an ongoing process that requires continuous monitoring and small improvements. It's best approached as a maintenance that, if done with proper testing, will give cumulative results. If ignored, however, the site's performance downgrade can hurt profits extensively.

Frequently Asked Questions

How can I tell if my website performance is bad?

A key performance metric is whether your site pages take more than three seconds to load. Other web performance indicators are high bounce rates, Core Web Vitals failing in the search console, low scores with tools like Google PageSpeed, site speed, and instability disparity between different mobile and desktop devices.

What causes a website to load slowly?

Common causes of poor load times are unoptimized images, excessive plugin use, bloated CSS and JavaScript files, too many HTTP requests, and a slow hosting provider. Most of these issues can be resolved by the owner to increase their page speed.

How long should a website take to load?

Ideally, a website's load time should not exceed two seconds, but loading under three seconds signals good site performance as well. Everything above three seconds is considered too slow, and conversion rates drop sharply with every additional second of delay.

What is the difference between website speed and website performance?

Site speed is a single metric measuring the load times of pages. Web performance is a broader metric covering not only page speed but also the website's user experience. It includes stability, interactivity, accessibility, and its impact on Search Engine Rankings. A website can load quickly and have poor performance.

Does website performance affect conversions?

Yes, data shows that there's a direct impact on conversion rates with a one-second delay, reducing them by up to 7 percent. It varies by niche and other factors, but generally, slow, unstable pages erode user trust in the website and its brand, resulting in visitors leaving.

Does website speed affect SEO rankings?

Yes. Google explicitly and officially uses page load speed as a ranking factor, especially for mobile devices. Performance factors like time to first byte and largest contentful paint are considered when showing results. A site can rank lower with better content but lower scores in such factors.