If you didn't hear of WebP yet, you should definitely check out Google's web site for it.
WebP is a format for images, in comparison with PNG it can be up to 26% smaller. And you can now use it for almost all browsers.
More detailed browser support data on Can I use.
AVIF actually even has a better compression as WebP. Read more on the official website.
More detailed browser support data on Can I use.
For this website, I use the @11ty/eleventy-img plugin to automatically generate optimized images.
Credits
Can I use graphics generated with https://caniuse.bitsofco.de.