Website Performance Guide
Core Web Vitals & Speed Optimization
Slow websites lose customers. Studies show 53% of mobile users abandon sites that take over 3 seconds to load. This guide explains what makes websites slow and exactly how to fix it. No technical background required.
Quick Summary
- ✓ Core Web Vitals are Google's official metrics for user experience, and they affect search rankings
- ✓ LCP under 2.5 seconds is the target for "good" loading speed
- ✓ Images are the #1 culprit. Unoptimized images cause 80% of slow page loads
- ✓ Every 1-second delay costs you approximately 7% in conversions
What Are Core Web Vitals?
Core Web Vitals are three specific metrics Google uses to measure how users experience your website. Since 2021, they're a direct ranking factor, meaning slow sites rank lower in search results.
LCP (Largest Contentful Paint)
How quickly the main content loads
Why it matters: Users perceive the page as "loaded" when LCP fires. Slow LCP = users leave before seeing your content.
INP (Interaction to Next Paint)
How responsive the page feels when clicked
Why it matters: Slow INP makes buttons and links feel "laggy" or broken. Users may click multiple times or give up.
CLS (Cumulative Layout Shift)
How much the page jumps around while loading
Why it matters: Layout shifts cause users to click the wrong thing or lose their place. Extremely frustrating on mobile.
Common Performance Issues (and How to Fix Them)
These are the issues we find most often when auditing websites. Each one directly impacts your Core Web Vitals and, consequently, your search rankings.
Unoptimized Images
CriticalImages not compressed or sized correctly are the #1 cause of slow websites. A single 5MB hero image can add 10+ seconds to load time.
Convert images to WebP format, resize to actual display size, and use lazy loading for below-fold images.
Render-Blocking JavaScript
HighJavaScript that loads before the page can display forces users to wait. Common with analytics, chat widgets, and ad scripts.
Add "defer" or "async" attributes to script tags, or move scripts to the bottom of the page.
No Browser Caching
HighWithout caching, browsers re-download everything on every visit. Returning visitors experience the same slow load as first-timers.
Set Cache-Control headers to cache static assets (images, CSS, JS) for at least 7 days.
Too Many Third-Party Scripts
HighEach third-party script (analytics, chat, ads, social) makes additional network requests and runs JavaScript that slows everything down.
Audit all third-party scripts. Remove unused ones. Load non-critical scripts after page load.
Uncompressed Text Resources
MediumHTML, CSS, and JavaScript files sent without compression are 3-5x larger than they need to be.
Enable GZIP or Brotli compression on your server. Most hosting providers support this.
Slow Server Response
MediumTime To First Byte (TTFB) over 600ms indicates server-side issues: slow database queries, shared hosting overload, or missing caching.
Upgrade hosting, enable server-side caching, optimize database queries, or use a CDN.
How to Test Your Website's Performance
You don't need technical expertise to check your site's speed. Here are the tools we recommend:
Google PageSpeed Insights
Free tool from Google that shows your Core Web Vitals and Lighthouse score. Tests both mobile and desktop.
pagespeed.web.dev →GTmetrix
Detailed waterfall charts showing exactly what's loading and when. Great for identifying specific bottlenecks.
gtmetrix.com →Blue Frog Full Audit
Our full audit runs Lighthouse on every page plus SEO, security, WCAG accessibility, and more. Results prioritized by business impact.
Get Full Audit →Chrome DevTools
Built into Chrome browser (F12 → Lighthouse tab). Best for developers who want to test changes in real-time.
Press F12 in ChromePerformance FAQ
Common questions about website speed and Core Web Vitals
Core Web Vitals are three metrics Google uses to measure user experience: LCP (loading speed), INP (interactivity), and CLS (visual stability). They directly affect your search rankings. Sites with poor Core Web Vitals rank lower in Google search results.
Lighthouse scores range from 0-100. A score of 90+ is considered good, 50-89 needs improvement, and below 50 is poor. Most business websites score between 40-70. Even improving from 50 to 70 can noticeably improve search rankings and user experience.
Mobile networks are slower and mobile devices have less processing power. Google also throttles mobile tests to simulate real-world conditions. Images not optimized for mobile, heavy JavaScript, and third-party scripts are the most common culprits.
Studies show that every 1-second delay in page load time reduces conversions by 7%. A site that loads in 1 second has 3x higher conversion rates than one that loads in 5 seconds. For e-commerce, slow sites directly cost you sales.
The three quickest wins are: 1) Compress and resize images (use WebP format), 2) Remove unused JavaScript and CSS, 3) Enable browser caching. These alone can often improve scores by 20-30 points with minimal effort.
Want Us to Audit Your Site?
Our full 847-checkpoint audit runs Lighthouse on every page and tells you exactly what to fix first. Performance, accessibility, security, competitive benchmarking.