What Is the Ideal Image Format and Compression Level for Optimized Images to Improve Largest Contentful Paint (LCP) Performance?


To optimize Largest Contentful Paint (LCP), it's ideal to use next-gen formats like WebP, AVIF or JPEG XR which offer superior compression and quality characteristics. The level of compression should be adjusted to balance visual quality and file size. A lower LCP time can significantly improve the user's perception of how fast your webpage loads. Implementing such techniques along with effective server response optimization, efficient asset delivery, and minimization of render-blocking resources can enhance the LCP performance substantially.

Image Format Optimization

Next-Generation Formats

Next-generation image formats such as WebP, AVIF, and JPEG XR offer superior compression, better quality characteristics compared to PNG or JPEG, while maintaining the same level of visual fidelity. For instance, WebP can offer 25-34% more compression compared to JPEG at the same quality level [WebP Compression Study, 2020].

Choosing the Right Format

While choosing an image format, it's critical to understand the type of image you're dealing with. For instance, photographs and complex illustrations tend to work well with JPEG or WebP, while simpler images, icons, or images with text can benefit from PNG or SVG [Which Image Format Do You Use?, 2020].

Image Compression Optimization

Adjusting Compression Levels

The compression level should be adjusted to provide a balance between visual quality and file size. This process involves compressing the image at different quality levels and comparing the resulting visual quality, file size, and load time. This can be done using various tools including Photoshop or online platforms like Squoosh [Optimize Images, 2020].

Using responsive images

Implementation of Responsive Images

Implementing responsive images using the srcset and sizes attributes allows the browser to choose the most appropriate image source based on the current viewport and device characteristics, further optimizing bandwidth and load times [Responsive Images, 2022].

Lazy Loading

Lazy loading is another technique to optimize image delivery. With lazy loading, you can defer loading offscreen images until they're needed, significantly improving initial page load time [Lazy Loading Images, 2020].


In conclusion to optimize LCP performance, it is recommended to use next-gen image formats like WebP, AVIF, or JPEG XR and adjust the level of compression according to the image type. Implementing other strategies like responsive images and lazy loading can also provide additional gains in improving LCP times.