12 Best Practices to Speed Up Website Performance on Mobile

Too often, site owners and their teams are fully immersed in their websites, only to miss one crucial question:

“How do site visitors experience my website on mobile?”

With Google’s introduction of its three Core Web Vitals (CWVs) in 2020—Largest Contentful Paint (LCP), First Input Delay (FID)*, and Cumulative Layout Shift (CLS)—failing to optimize your website for mobile access can quickly result in disastrous rankings that lead to poor visibility and can hamper lead generation and conversion rates. 

 

These three metrics are the standard for excellent user experience and must be kept at the forefront of your mind when it comes to developing and maintaining your website. 

And, considering that mobiles currently account for around half of all website traffic globally, making sure that your website loads rapidly and correctly on those traffic-heavy devices should be a no-brainer.

One thing to keep in mind, however, is that CWVs come in handy only when a site's competitors all have the same quality of content; it’s at that point that metrics such as loading speed become the deciding factor.

Image sourced from statista.com

This guide will explore 12 ways to speed up your website performance on mobile and explain exactly why this is crucial.
 

The importance of fast website performance on mobile

As seen above, mobile traffic accounts for more than half of total online traffic, and page speed is part of the metrics that Google uses to evaluate website quality.

If we combine these two factors, we get a simple picture: 

Ensuring your website loads quickly on mobile devices will help your SERP rankings, visibility, and potentially even your lead generation and conversions.

The importance of rapid website performance is highlighted in the following research and statistics:
 

Increased lead generation and sales

• Improving website speed by as little as 0.1s may bring nearly 26% more users to fill out and submit a web form, thus increasing lead generation rates.
• Faster page load can translate into more sales, as Vodafone Italy demonstrated. The company created a Web Vitals-focused mobile version of its website and found that, compared to the non-optimized one, it led to an 8% increase in sales.
   

Increased interaction and engagement

• In a collaborative study with Google, Deloitte found that a mere 0.1s improvement in loading speed affects the entire buyer’s journey. Offering a 0.1s faster ecommerce website with a smooth browsing experience encourages users to stay longer, leading to up to 8.6% more pages viewed in a session.

• Slow-loading websites often frustrate users and lead them to 'bounce' before the site fully loads. If you improve your online store’s LCP, users can view and interact with your content more quickly, making them 8.3% less likely to go to your competitors.
   
• With 44% of online shoppers who tell friends and family about a bad online shopping experience, you can’t settle for anything less than “delightful.” Optimizing for speed, responsiveness, and interactivity ensures your online store sees a 5.2% improvement in customer engagement for every 1-millisecond boost in load speed.

Bear in mind that there are lots of ways to optimize your site. For instance, you can search for the perfect, on-brand domain name using domain name search and keep up with changing search engine optimization (SEO) best practices. 

That said, as we mentioned, CWVs become the deciding factor when content quality is the same across websites.

It’s also good to know that better Core Web Vitals have been linked to improved search engine advertising (SEA) results. In fact, one of Lever Interactive's clients increased their Quality Score, leading to -17% CPC and -31% CPA, which also meant a 20% increase in conversion rates on faster landing pages.

Moreover, Netzwelt saw advertising revenues increase by 18%, ad visibility increase by over 75%, bounce rates decrease by 50%, and page views increased by 27% by optimizing for Core Web Vitals.

Boost ROI with passed Core Web Vitals! Get started with NitroPack for free →

What affects mobile performance?

All things considered, it’s pretty clear how important it is to have a fast website performance for mobiles. But what are the types of things that are slowing your website down? The following can be at fault:

• Unoptimized images
• Javascript issues
• Too many ads
• Not using a strong hosting provider
• Not using GZIP compression
• Too many HTTP requests
• Overly complicated content

If any of the above rings true for you, then this guide is exactly what you need. 
 

How to Measure Your Site's Performance and Speed on Mobile 

Given what you know now, you’re probably wondering what the best ways are to speed up mobile website performance and whether you’ll need to be a mobile developer to achieve it.

But before we dive into our ultimate guide of tips, it’s wise to discuss how fast your mobile website should be and how you can measure your site’s performance and speed. 

In other words, how do you know what to aim for?

According to Scaleflex, the “unified benchmark since 2015” has been that a webpage should take 2 seconds to load. But with an average load time for mobile sites of 8.6 seconds, it’s clear that there’s a lot of work to do.

Thankfully, tools are available to audit your mobile site and determine what needs improvement. 
 

PageSpeed Insights

PageSpeed Insights (PSI) is a site performance testing tool that analyzes load time, responsiveness, and visual stability for a specific webpage on mobile and desktop.

You should pay particular attention to Core Web Vitals, as these field data-based metrics measure how real users experience your website rather than hypothetical users. 

The following three Core Web Vitals are the essential metrics to analyze, as they will tell you a lot about your mobile performance:

• Largest Contentful Paint (LCP): how much time it takes for the largest visual element on a site to be fully displayed. According to Google, this should be around 2.5 seconds (or less). 
• Interaction to Next Paint (INP): a measurement of a web page's responsiveness, quantifying the delay between a user interaction (like a click, tap, or key press) and the visual response or update to the page. A good INP score is below 200ms.
• Cumulative Layout Shift (CLS): a measurement of a website’s visual stability. A good CLS score should not exceed 0.1.
   

Chrome DevTools

DevTools are built directly into Google Chrome and are great for debugging and optimizing your website. When it comes to mobile performance, these key features are particularly useful:

• Device Mode: This mode enables the simulation of a mobile environment within Chrome and allows developers to anticipate how a site will operate across various mobile devices without requiring physical hardware for testing.
• Network Throttling: This feature allows developers to mimic different network speeds to understand how a website performs under constrained internet conditions. This allows for the optimization of load times and overall responsiveness.

Image sourced from developer.chrome.com

Even after optimizing your mobile website, you will still need to continuously test and monitor your mobile page according to different metrics. 

Do remember that, ultimately, mobiles will never load a website as fast as a desktop. For this reason, mobile results are always lower than desktop ones. However, don’t let this put you off; you’re not competing against desktops—you’re competing against other mobile webpages. 

That is why it is so important for site owners to focus on optimizing their website within the context of CWVs as a key standard. 

And this is how you can do it…
 

5 Best Techniques to Speed Up Mobile Website Performance 

1. Optimize images and font usage for mobile

Unoptimized images and fonts are heavy and will cause your website to lag. 

LCP is a key Core Web Vital metric used to measure perceived load speed. 

70% of mobile pages have an image as an LCP element. According to Google PSI, there are some image and text-related recommendations to take into account when looking to speed up mobile site performance.

• Properly size images
• Efficiently encode images
• Serve images in next-gen formats
• Enable text compression
• Ensure the text remains visible during webfont load
• Keep request counts low and transfer sizes small
• Ensure that image elements do not have explicit width and height
• Avoid enormous network payloads

Other image and font optimization recommendations include using next-gen image formats rather than older ones, such as JPEG or PNG. Next-gen image formats like WebP offer superior compression—a higher image quality with less data. 

For those of you hosting ecommerce sites, you can hardly reduce the number of images on your site: they’re your main marketing tool for attracting consumers.

If that’s the case, you’ll need to pay extra attention when optimizing e-commerce images, such as ensuring the correct image format.

You can also use different images for desktop, mobile, and tablet. This is a bit more labor-intensive, but it ensures that each medium is tailor-made for its audience.
 

2. Leverage mobile server caching

Caching is the technique used by browsers to store a page’s content in local storage. This is highly useful for visitors to your website, as it means they don’t have to download the same data every time they click on your homepage.

Enabling browser caching will help reduce loading time. It also reduces bandwidth consumption, cuts the number of requests to a server, and provides the visitor with a much better user experience.

Essentially, opting for a reliable caching technique will ensure repeat visitors have a smooth and seamless experience when using your website.

In the specific context of mobile page speed, you’ll want to enable server caching. Generally speaking, your server host will have taken care of that by providing a built-in server caching function with your web hosting plan.

If this isn’t the case, and you’re considering switching your host provider, you should select a provider that also supplies optimized configurations for mobile platforms and scalable resources to handle varying traffic levels efficiently. So you have everything you need for better mobile performance.
 

3. Streamline mobile server response time

Server response time is a metric that describes the time it takes for a device to receive feedback from the server once a request has been sent to load a web page. This response time is measured by TTFB (Time To First Byte). In essence, TTFB measures the time it takes for your website to respond to requests.

Image sourced from gtmetrix.com

When users visit a website, all content, including texts, graphics, and source code, is processed by a server. The more content the website contains, the longer it takes for the server to process, resulting in an increased website loading time.

To counteract this, you can:

• Use GZIP compression to reduce the weight of your website and improve its loading time
• Minify CSS, HTML, and JavaScript and get rid of extra (and heavy) code
• Remove render-blocking resources, which are usually inline CSS or JavaScript that a server tends to prioritize before processing other aspects of the webpage you’re trying to load.
• Invest in more robust hosting
• Use a content delivery network (CDN)
• Review third-party scripts
   

4. Minimize mobile page redirects

Of course, redirection is useful if you need to tell a search engine to find the site at another address. Alternatively, you may want to eliminate issues with subpages and bad links.

Do note that too many redirects can affect how quickly your website loads. As such, redirects should be kept to a maximum of one per link. Any website visitor who is redirected to another page will have to wait more time to get there.

Avoid this by reducing unnecessary redirections from your main page. You may not be able to get rid of all of them, but a quick audit should help you identify non-essential ones.
 

5. Monitor your mobile page speed continuously

Lastly, regularly monitoring your mobile page speed is essential if you want to keep up the good work you’ve done so far, as well as take swift action in case you spot any issues. Consider incorporating these lab-based metrics into your monitoring:

• Time To First Byte (TTFB): the amount of time it takes for a browser to receive the first byte of information. Aim for no more than 200 milliseconds (or 100 milliseconds for static content).
• Total Blocking Time (TBT): the amount of time between First Contentful Paint (FCP) and Time to Interactive (TTI). Ideally, you’ll want this to be under 200 milliseconds.
• First Contentful Paint (FCP): the time between a page starting to load and when the page’s content is available on screen. This should be no more than 1.8 seconds. 

By monitoring these metrics, you’ll have access to a precise table of data that will indicate where, if at all, you’re going wrong. Do keep in mind that monitoring both lab and field-based metrics is the best way to analyze loading speed and user experience, so don’t forget to pay attention to field-based metrics, too.
 

7 Bonus Mobile Speed Optimization Strategies for WordPress

“Why is my WordPress site so slow?”

You’re not alone in this head-scratcher. In fact, WordPress is infamous for how quickly a website can bloat due to excessive resources and unoptimized themes and plugins. Here’s how to address this.

Implement lazy loading for improved performance

If your website is taking 20 seconds to load due to one or two images that aren’t even visible until visitors scroll way down, then lazy loading could be the trick for you.

Lazy loading uses special scripts that help delay the loading of images, videos, or graphics that are not immediately displayed to users. 

To get started with lazy loading, try out the NitroPack Lazy Loading feature.
 

Minimize HTTP requests to boost mobile site speed

Whenever someone visits your website, the browser is required to request many different files, which are otherwise known as HTTP requests.

Naturally, these HTTP requests impact how quickly your page is able to load. You can minimize HTTP requests by:

• Deleting unnecessary images.
• Reducing image size.
• Minifying CSS and JavaScript files.
• Combining CSS and JavaScript files.

You can also implement lazy loading—as seen above—and use a Content Delivery Network (CDN).
 

Utilize Content Delivery Networks to reduce device latency

A Content Delivery Network (CDN) is a network of proxy servers and their data centers that are geographically distributed. 

They help improve content delivery, performance, and quality by caching web content (e.g., pages, images, and videos) in proxy servers close to your location.

You may also want to explore mobile CDNs. These aim to enhance content delivery, specifically on mobile and wireless networks. As such, they aim to greatly improve website performance.

However, be aware that privacy may be an issue. In that case, .env files are a useful way of keeping sensitive information away from the cloud and locked up in a key-value format.

Reduce render-blocking resources

Render-blocking resources are bits of code in website files, such as CSS and JavaScript, that are used to prevent a web page from loading too quickly.

When you load a page, the browser parses its HTML. If it encounters CSS and JavaScript files, it has to both download and parse these too. This inevitably means the page takes longer to load.

If the page doesn’t parse these resources, it’s able to load quicker. Therefore, exploring render-blocking resources improves website loading and user experience. To find out how to identify and eliminate render-blocking resources without using any plugins, check out this comprehensive guide.
 

Use resource hints for faster performance

Resource hints are instructions that let the browser know how to handle particular resources or web pages. These hints can be used to tell the browser which resources should be prioritized.

You can integrate the HTML code snippets on your website that correspond to the elements that need to be prioritized into your site page; this will have the browser start loading the selected files sooner than if it was finding them through the normal course of loading the page.

Different resource hints can be used for different purposes; below are two examples:

• Prefetch: This hint lets the browser fetch resources that might soon be needed and store them in the cache.
• Preload: This makes the browser download a resource quicker than the browser would discover because it is a key element of the page.

If you want to learn more about the resource hints, check out our comprehensive guide.
 

Explore Accelerated Mobile Pages (AMP) and Progressive Web Apps (PWAs)

Accelerated Mobile Pages (AMP) is an open-source technology that was developed in 2015 to help enhance immediate web page development. Its main purpose is to reduce pages to their most crucial parts, storing the cached version on Google servers to optimize server performance.

Progressive Web Apps (PWAs) focus more on user experience and interaction. They aim to make mobile websites more closely resemble the apps on your smartphone.

They help your web page load faster. However, there is the potential for lag and high battery consumption as they run on a third-party browser. So, you’ll have to investigate to figure out which is appropriate for your mobile website.
 

Consider AI speed optimization tools

Incorporating AI into website speed optimization is increasingly significant. This is because AI tools can significantly reduce load times by predicting user behaviors to create sophisticated caching methods and pre-load pages or assets before users even click on them. 

Additionally, they can be used to automate tasks such as automatically resizing and compressing images and improving code efficiency by continuously monitoring and optimizing performance in real-time.

One such tool is Navigation AI by NitroPack.

Navigation AI is an AI-powered web browsing optimizer that actively predicts and analyzes user behavior to prerender entire pages during the customer journey. 

It allows site owners, regardless of their platform, to offer instant browsing experiences on both desktop and mobile, boosting customer engagement and conversion rates along the way.

The way Navigation AI does it is by using Speculation Rules API:

• Firstly, it applies AI-enhanced initial predictions on page load based on data without passing it over to the Speculation Rules API (to not overwhelm the browser).
   
• Secondly, it analyzes the user behavior, adjusting the predictions, and instructing the Speculation Rules API to prerender (or prefetch) a page once we’re sure what the following action will be.

This predictive page loading leads to the following:

1. Loading times under 3 seconds. 
2. Massive improvements in LCP and CLS.
3. Better Core Web Vitals for the entire website. 

Conclusion

With mobile traffic accounting for nearly half of all website traffic on a global scale, it should be clear by now that optimizing your mobile website performance is crucial.

Follow our tips above and apply the mentioned optimization techniques to reap important benefits, such as increased user engagement with your website, as well as increased lead generation and sales. 

We’re certain that with a bit of time, effort, and focus, your mobile performance will outstrip all competitors.