Why Images Kill Your LCP Score
Largest Contentful Paint (LCP) measures how long it takes for the biggest visible element to render. On most pages, that's an image. Google considers LCP under 2.5 seconds "good" — over 4 seconds is "poor" and will hurt your rankings.
The Image Optimization Checklist
1. Use Modern Formats (WebP/AVIF)
Switch from JPEG/PNG to WebP for an instant 25-35% file size reduction with no visible quality loss. Use our JPG to WebP Converter for quick conversion. Serve AVIF where supported for even more savings.
2. Resize to Display Dimensions
Don't serve a 4000px image that displays at 800px. Resize images to their actual display size (accounting for 2x retina: serve 1600px for an 800px display).
3. Compress Aggressively
JPEG quality 80% is visually identical to 100% but significantly smaller. Compress every image before uploading. For target file sizes, use Resize by KB.
4. Lazy Load Below-the-Fold Images
Add loading="lazy" to every image that isn't in the initial viewport. This prevents below-the-fold images from competing with your LCP image for bandwidth.
Exception: Never lazy load the LCP image itself — it needs to load as fast as possible.
5. Preload the LCP Image
Add a <link rel="preload"> tag for your hero/LCP image. This tells the browser to start downloading it immediately, before it even parses the CSS.
6. Set Width and Height Attributes
Always include width and height on <img> tags. This prevents Cumulative Layout Shift (CLS) — another Core Web Vital — by reserving space before the image loads.
7. Use Responsive Images (srcset)
Serve different image sizes for different screens. A mobile user on a 375px screen shouldn't download the same image as a 1440px desktop user.
8. Strip EXIF Metadata
EXIF data adds kilobytes to every image with zero user benefit. Remove it to shave off extra bytes.
Test Your Score
After optimizing, test with Google PageSpeed Insights or Lighthouse. Focus on the LCP metric — it should be under 2.5 seconds on mobile. Also check your alt text with our Image Alt Checker to make sure you haven't missed any accessibility.