HTML SVG

A photo in PNG or JPEG format is a grid of colored dots, called pixels. When you enlarge it beyond its size, the browser has to stretch each dot, and the edges turn blurry and jagged. An image can also be stored as a description instead: "a yellow circle, centered here, with this radius, and a green outline." The browser draws that description fresh at whatever size the page needs, so the edges stay sharp. An image stored as shapes is called a vector graphic, and the format the web uses for it is SVG, short for Scalable Vector Graphics.