This thesis explores responsive images for websites, i.e., content images that respond to users display size, pixel density and bandwidth. We look into responsive web design and how it is related to responsive images. Different responsive image techniques are discussed and various use cases for responsive images are explored along with technologies that are needed to implement responsive images. A testing website is built and responsive image techniques are applied one by one, tested and compared and its effect on the websites load time is measured. The process of implementing the techniques is described with code examples and images. The results indicate that responsive images can certainly have positive effect on loading time of a website. Weather or not responsive images should be implemented depends on how much image data the website has and how fast the Internet connection is. Websites with more images can certainly profit from using responsive image techniques, especially if only slower bandwidths are available.