Check your website with a Lighthouse audit.
Check out the critical resources of your website using the WebPageTest tool (recommended by Google).
To optimize your critical resources, use the Google guide Optimizing the visualization process .
To optimize your images, use recommendations from Google Web Fundamentals Responsive Images . Here it may be useful to pay attention to the fact that you assign different image files for different media queries or image formats using the picture element. For example:
<picture> <source media="(min-width: 800px)" srcset="head.jpg, head-2x.jpg 2x"> <source media="(min-width: 450px)" srcset="head-small.jpg, head-small-2x.jpg 2x"> <img src="head-fb.jpg" srcset="head-fb-2x.jpg 2x" alt="a head carved out of wood"> </picture>
You can also use the following code, which will allow the browser to automatically calculate the optimal pixel density and select the correct image to load using the srcset element:
<img src="lighthouse-200.jpg" srcset="lighthouse-100.jpg 100w, lighthouse-200.jpg 200w,lighthouse-400.jpg 400w, lighthouse-800.jpg 800w, lighthouse-1000.jpg 1000w, lighthouse-1400.jpg 1400w, lighthouse-1800.jpg 1800w" alt="a lighthouse">
Please note that currently the lightest images are JPG (JPEG) images. You can use the Photo Editor PIXLR tool to change the image format and to change the image size .
The ImageOptim tool can be useful for compressing images.