I'm thinking the pictures on my website are too large and heavy. I was looking for the best resolution and quality to export my pictures. I found some information that says 72dpi is enough resolution for a website but I didn't find any information about the quality and size.
I would like to know what is the best resolution, size and quality to have a nice picture that is not too big.
The best resolution for a normal website is exactly 1-to-1.
IE you want to display an image at 200 pixel width, you should save it to 200 pixel width. forget DPI as its entirely irrelevant when displayed on screen.
Quality (JPG) should be as low as possible without affecting the image quality too much, usually around 65-85% - of course it depends on the site, a photographers' site would want higher quality than a forum, for example.
What is the best resolution and quality for website
The answer is that there are, and must be, several per image.
You should consider using a responsive web-design and using HTML5 and CSS3 to serve up a version of the image suited to the size and resolution of the viewing device.
The optimum image for an iPhone is different to that for a 22" desktop screen.
See Responsive image design and Fluid images
Note that the Google search engine, when used from a mobile device, prioritises web-sites that meet Google's "mobile-friendly" guidelines.
In practice this means having a range of image sizes available and enabling the browser to only download the minimum sized (in bytes) image needed.
Here is one reference.
The best resolution is an evolving standard. Not just in terms of sizes but also the depth and quality of images displayed change as new displays and devices are invented. When 2K and 4K monitors become common, current sizes will not be optimum. In any case, most common maximum sizes today are for wide screens pixel dimensions of 1366 x 768, 1600 x 1200, etc. As for size and quality, most photographers want the maximum possible. You have to balance that with your web service speed and page load times.
