Your website’s speed is not a technical detail. It’s a business metric. Every second of load time costs you money — and the numbers are worse than most people realise.
The data is clear
Google, Amazon, and Walmart have all published studies on the relationship between page speed and business outcomes. The findings are consistent:
- Amazon found that every 100ms of added latency cost them 1% in sales
- Google reported that a 0.5-second increase in search page load time caused a 20% drop in traffic
- Walmart saw a 2% increase in conversions for every 1-second improvement in load time
- BBC lost 10% of users for each additional second of load time
These aren’t edge cases. They’re patterns that apply to every website, at every scale.
Where you lose people
The critical window is 0-3 seconds. Here’s what happens:
Under 1 second: The site feels instant. Users engage naturally, explore freely, and convert at the highest rates. This is where you want to be.
1-3 seconds: Acceptable for most users, but attention starts to drift. Some visitors will bounce before the page finishes loading, especially on mobile.
3-5 seconds: You’ve lost a significant portion of your audience. Studies show 53% of mobile visitors leave a site that takes longer than 3 seconds to load.
Over 5 seconds: Most users are gone. The ones who stay are likely comparing you to competitors — and they’re already frustrated.
The Google penalty
Since 2021, Google has used Core Web Vitals as a ranking factor. Slow sites rank lower. This creates a compounding problem:
- Your site is slow, so Google ranks it lower
- Lower ranking means less traffic
- Less traffic means fewer conversions
- Fewer conversions mean less revenue to invest in improving the site
Meanwhile, your faster competitor climbs the rankings, captures your traffic, and grows. The gap widens over time.
The three metrics Google cares about:
- Largest Contentful Paint (LCP): How quickly the main content appears. Target: under 2.5 seconds.
- First Input Delay (FID): How quickly the page responds to interaction. Target: under 100ms.
- Cumulative Layout Shift (CLS): How much the page jumps around while loading. Target: under 0.1.
What makes websites slow
Most slow websites share the same problems:
Too much JavaScript
The average web page in 2026 ships over 500KB of JavaScript. On a mid-range mobile device, that takes 3-4 seconds just to parse and execute — before any content appears.
The culprit is usually a JavaScript framework (React, Angular, Vue) combined with multiple third-party scripts (analytics, chat widgets, marketing pixels, A/B testing tools). Each one adds weight.
Unoptimised images
A single unoptimised hero image can be 2-5MB. That’s more data than most entire web pages should be. Yet many sites serve full-resolution images to mobile devices on slow connections.
Render-blocking resources
CSS and JavaScript files that block rendering prevent the browser from showing anything until they’ve fully loaded. A single slow-loading stylesheet or script can delay the entire page.
Slow server response
If your server takes 500ms to generate a response, your page can never load in under 500ms — no matter how optimised everything else is. Cheap shared hosting, unoptimised database queries, and bloated CMS platforms are common causes.
What to do about it
Measure first
You can’t improve what you don’t measure. Run your site through Google PageSpeed Insights and note your scores. Check your Core Web Vitals in Google Search Console for real-world data from actual visitors.
Ship less JavaScript
This is the single highest-impact change for most sites. Audit your JavaScript: do you really need that animation library, that carousel plugin, that chat widget? Every script you remove improves load time.
Better yet, choose a technology that doesn’t require shipping a JavaScript application to the browser. Server-rendered approaches like Phoenix LiveView deliver rich interactivity with kilobytes of JavaScript instead of megabytes.
Optimise images properly
Convert to WebP or AVIF. Serve responsive sizes. Lazy load everything below the fold. Set dimensions to prevent layout shift. This alone can cut page weight by 50-80%.
Use a CDN
Serve static assets (images, CSS, JavaScript, fonts) from a content delivery network. This puts your files on servers close to your visitors, reducing latency from hundreds of milliseconds to single digits.
Choose fast hosting
Your server should respond in under 200ms. If it doesn’t, upgrade your hosting or optimise your application. For static sites, use edge hosting (Cloudflare Pages, Vercel, Netlify). For dynamic applications, choose a provider with servers near your audience.
The investment case
Improving your site’s speed from 4 seconds to under 2 seconds typically costs far less than the revenue you’re losing from slow load times. For an e-commerce site doing €100,000/month, a 2% conversion improvement from speed optimisation is worth €2,000/month — €24,000/year.
For lead-generation sites, the math is similar. More visitors stay, more visitors convert, more leads enter your pipeline. The ROI on performance work is almost always positive.
How we approach performance
At Linjerum, performance is not an optimisation step — it’s the foundation. We build with Phoenix LiveView, which renders HTML on the server and sends minimal JavaScript to the browser. Our sites typically achieve PageSpeed scores above 95 and load in under one second.
We don’t add performance as an afterthought. We start with it.
If your current site is underperforming, we offer performance audits that identify exactly what’s slowing you down and what it would take to fix it. Contact us at support@linjerum.com.