LCP

Category: Design

What is LCP?

Largest Contentful Paint (LCP) is a performance metric that measures the time it takes to load the largest visual element in the viewport of a web page. This element can be an image, video, or text block.

LCP is one of the key metrics in Core Web Vitals by Google and directly affects user experience and SEO.

Why is LCP important?

  • Accepted loading speed

    Users perceive the page as loaded when they see the main content

  • User experience

    Fast loading of the main content improves user satisfaction

  • SEO impact

    Google uses LCP as one of the key factors for ranking in the search engine

  • Business metrics

    Good LCP leads to a lower bounce rate and higher conversion

Elements that LCP measures:

Images

  • IMG elements
  • SVG elements inside IMG
  • Poster images of video

Video elements

  • VIDEO elements
  • Thumbnail images

Elements with background image

  • Elements with CSS background-image
  • Block-level elements

Text blocks

  • Paragraph elements (p)
  • Heading elements (h1-h6)
  • DIV elements with text

Standards for LCP evaluation:

Good &lte; 2.5 seconds

The page loads quickly and provides excellent user experience

Needs improvement 2.6 - 4.0 seconds

There are opportunities for optimization of loading speed

Weak > 4.0 seconds

The page loads too slowly and needs significant improvements

How is LCP measured?

  1. Start of loading

    LCP time starts from the moment of navigation start

  2. Discovery of candidates

    The browser identifies potential LCP elements

  3. Rendering in viewport

    The element must be visible in the viewport

  4. Final LCP

    The browser determines the largest element and the time it takes to load

Common reasons for bad LCP:

Slow server responses

Problem: The server takes too long to process requests

Solution: Optimize server code, caching, CDN

Render-blocking resources

Problem: CSS and JavaScript files block rendering

Solution: Critical CSS, async/defer scripts, code splitting

Slow loading of resources

Problem: Large images and media files

Solution: Image optimization, lazy loading, modern formats (WebP)

Slow client rendering

Problem: Too much JavaScript to execute

Solution: Minimize JavaScript, optimize code

Techniques for optimizing LCP:

Server optimizations

  • Caching server responses
  • CDN usage for static resources
  • Gzip/Brotli compression
  • Database optimizations
  • HTTP/2 or HTTP/3 implementation

CSS optimizations

  • Critical CSS inline - placing critical CSS in head
  • Minimize CSS
  • Remove unused CSS
  • CSS delivery optimization

JavaScript optimizations

  • Async/defer attributes for scripts
  • Code splitting and lazy loading
  • Minimize JavaScript
  • Tree shaking for removing dead code

Images and media

  • Image compression and optimization
  • Modern formats (WebP, AVIF)
  • Responsive images with srcset
  • Lazy loading for images outside the viewport
  • Preload important resources

Tools for measuring LCP:

  • Google Lighthouse Full performance check including LCP
  • PageSpeed Insights Online tool for analyzing LCP and other metrics
  • Chrome DevTools Performance panel for detailed analysis of LCP
  • Web Vitals Extension Browser extension for real-time measurement
  • Google Search Console Core Web Vitals report for the entire site

Good practices for LCP:

  • Prioritize critical resources - preload important images
  • Optimize server response - target TTFB under 200ms
  • Reduce resource size - compress images and code
  • Eliminate render-blocking resources
  • Use caching effectively
  • Test regularly - monitoring LCP over time
  • Optimize for mobile devices - most problematic

Conclusion:

LCP is a critical metric that directly reflects how quickly users see the main content of your page. By focusing on optimizing LCP, you not only improve user experience, but also increase SEO results and business metrics on your website.

Goal: Aim for LCP under 2.5 seconds for optimal user experience.