Which quality of images should be used in a web page so that it has a good seo???

Question

when we use images in our web page....what should be it's quality and optimal size so that it does not affect it's loading time and SEO

Answer 1

Use jpg images when you mainly care about storage and loading size.
(But note that their quality drops as the picture gets larger. Quality drops too each time you edit them)

Use Png if you care more about quality. (The file size is not significantly higher, but it can make a difference between >1MB picture or not sometimes. )
^ It supports transparency/alpha too, unlike jpg.

tiff if you care about quality too, but its uncompressed format unlike png.

So? Just use smaller jpeg for all smaller images. No one is going to notice the quality difference (to the naked eye at least)
For larger images, I suggest PNG, but you still can use jpg if you see it as fine to you.

Answer 2

Vector images ;) compress and serve scaled. Define image size and make sure you have an alt tag. You will see a slight increase in speed and SEO.