100% Private100% PrivateImage Guide
Most uploaded images are far larger than they need to be. A 4000-pixel photo displayed at 800 pixels wide still costs the full download time. Resizing to the display size is the single biggest speed win for most blogs.
Find the display size first. A blog content image is usually 800-1200 pixels wide, a product image 1000 pixels, a thumbnail 800 pixels. Resize to that width, not to a random smaller size, or the image will look soft when the page scales it up.
Keep aspect ratio on. Stretching an image to fit a box distorts products and faces, and readers notice it instantly. If you need a different shape, crop it, do not stretch it.
Resize before you compress. A smaller image compresses to a smaller file, and you get two wins from one pass.