Images significantly impact website performance, often being the largest files that can slow down loading times and affect user experience via metrics like LCP and CLS. Developers frequently focus on optimizing JavaScript and CSS, neglecting images. Selecting the right format is vital—JPEG for photos, PNG for graphics, and newer formats like WebP and AVIF for efficiency. Additionally, responsive images tailored to the user’s device can vastly improve load times, minimizing unnecessary data consumption. Implementing appropriate HTML tags like <picture> with srcset allows the browser to choose the best image based on the device.
Images are the biggest performance bottleneck on websites, impacting LCP and CLS, yet are often overlooked during optimization compared to JavaScript and CSS.
Choosing the right image format is crucial—JPG, PNG, WebP, and AVIF serve different needs, with modern formats typically offering improved speed and efficiency.
Implementing responsive images allows developers to serve the appropriate image size for different devices, enhancing load times and reducing data consumption.
Using attributes like srcset and sizes in a <picture> tag enables browsers to load the most suitable image for the user’s device, optimizing performance.
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