If you upload very large images to your website, your website will slow down when those images are viewed by your visitors.
The solution is to learn how to optimise (trim images down to size) before you upload them.
Preparing images involves reducing the physical size and file size, while still leaving the images looking good. Nobody wants tiny, grainy images on a website, and it isn’t necessary.
Sizing your images to 1,280 px wide is a good target for many websites.
Statistically, if you size your images to 1280 px wide, in 93% of cases the images will be large enough to fill your visitor’s browser. Any larger and the image will be squeezed down in width anyway.
When you upload an image, WordPress not only uploads the original image, it automatically creates three resized images for you:
- a Large version (default 600px)
- a Medium version (default 300px)
- a Thumbnail (default 150px)