Do `<img>` that are smaller than the original still load the entire image file?

[zinfeflalyday]

When I have an \[code\]<img>\[/code\] that is smaller than the original image, will the file automatically be resized? Or will the user have to load the entire image?For example, I have giant wallpaper files, but I only show thumbnails that are 100px by 100px. Am I doing something inefficiently by just setting the \[code\]<img>\[/code\] width and height to 100px?