LCP
Largest Contentful Paint
4.6s
Poor
Good: < 2.5s
Measures how long it takes for the main content to appear on screen
Optimize Forced Reflows Performance
How to optimize lkv.cz
Optimize Forced Reflows Performance
Medium Impact+8 points estimated
Why It Matters
Forced reflows in productsList.js block the main thread for 173ms, causing poor interactivity and delayed Time to Interactive.
How to Fix
Batch DOM reads and writes in productsList.js to avoid layout thrashing. Cache geometric property reads like offsetWidth instead of querying them repeatedly. Use requestAnimationFrame for DOM updates that affect layout.
0Needs Improvement
What This Score Means
A score of 80 falls in the "Needs Improvement" range (50-89). While it is better than poor (0-49), you should aim for 90+ to provide an optimal user experience and maximize SEO benefits.
This site is slower than approximately 35% of similar sites. The main issues affecting performance are image optimization, JavaScript execution time, and layout stability.
Addressing these issues could improve your conversion rate by 15-20% and boost your search engine rankings.
Core Web Vitals Analysis
INP
Interaction to Next Paint
26ms
Good
Good: < 200ms
Measures how quickly the page responds to user interactions
CLS
Cumulative Layout Shift
0.11
Needs Improvement
Good: < 0.1
Measures visual stability - how much content shifts during page load
AI Performance Analysis
This e-commerce site has decent performance with a score of 80/100, but suffers from significant layout stability issues. The biggest problem is a poor Cumulative Layout Shift score caused by an unsized image element and web font loading, which creates a jarring visual experience as content jumps around while the page loads. The site also has a slow Largest Contentful Paint of 4.6 seconds due to excessive unused CSS (29 KiB) and JavaScript (81 KiB) that could be removed. Fixing the image sizing issues and cleaning up unused code could improve both the visual stability and loading speed substantially.
Other Optimization Recommendations
Fix Image Layout Shifts
High Impact+25 points estimatedWhy It Matters:
Unsized images cause significant layout shifts with a CLS score of 0.115, severely impacting user experience and Core Web Vitals.
How to Fix:
Add explicit width and height attributes to all images, especially the category menu image and footer logo. Preload the Muli-Light.woff2 font using <link rel='preload' href='https://www.lkv.cz/assets/front/fonts/Muli-Light.woff2' as='font' type='font/woff2' crossorigin> in the HTML head. Reserve space for images using CSS aspect-ratio or min-height properties.
Reduce Unused JavaScript and CSS
High Impact+18 points estimatedWhy It Matters:
Unused resources waste 110+ KiB of bandwidth and delay LCP by 150ms each for JavaScript and CSS.
How to Fix:
Remove or defer the unused fancybox.js which wastes 83KB (99% unused). Split your main CSS file to load only critical above-the-fold styles initially, deferring the remaining 29KB of unused CSS. Use code splitting to load JavaScript modules only when needed.
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Related Performance Analyses
More Generic Speed Tests
Generic Performance Resources
Optimize Logo Image Delivery
The oversized logo image wastes 97 KiB and delays LCP by 450ms while being displayed much smaller than its actual size.
Remove Unused JavaScript Code
126 KiB of unused JavaScript from Google Analytics and GTM delays LCP by 900ms and wastes bandwidth.
Eliminate Render Blocking Resources
Render blocking CSS and fonts delay LCP and FCP by 1,050ms, preventing users from seeing content immediately.
Fix Image Sizing and Compression
Award images are oversized by 441KB and lack explicit dimensions, causing layout shifts.