Also known as a linked image, an external image is a picture or graphic that a website accesses and displays from another server or a different domain. An external image is in contrast with a local or internal image, which is an image that is located on the same server as the website's main files. Some webmasters link to external images to reduce hosting costs or to organize web file types on different servers.
A server is a machine that provides data to other computers. On the web, a server holds information about the website, which a user can access by inputting the web address into the address bar of a web browser. Generally, external images are used by webmasters and web designers creating websites made with images located on a different server than the server that hosts the hypertext markup language (HTML) code that shapes the website. Some websites use a separate domain and server to hold site data separately from HTML files.
External image linking can be a problem for some websites that host images. Webmasters at other websites can program their sites to display the images from the original site on which it is hosted. This means of displaying images is often frowned upon because the linking site is showing content that does not belong to the site, and is essentially stealing bandwidth from the site where the image is hosted.
When a site uses an external images without permission, the linking site's webmaster does not have to pay to host the image, but the site that originally hosted the image may have to pay extra charges for the web data, called bandwidth, that the linking site's visitors used. Most hosting sites prefer linking sites ask permission to use an external link or host the image on their own servers. To prevent unsavory webmasters from leaching bandwidth by displaying an external image, some hosts use server programs that disable image display on external websites, often replacing the original linked image with one berating the webmaster for linking or referring the viewer to the original site for the image.
Low-budget webmasters can use external image linking to save money on hosting services by hosting pictures on a free picture hosting site. Often, free web hosting has limits on the amount of data, including pictures, movies, and HTML files, a user can upload onto their server. When a webmaster runs out of room on a server, hosting images off site, either on another free website or a free picture-hosting service, can ethically extend the webmaster's available web space.