Inline linking

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Inline linking, also known as hotlinking, leeching, or direct linking is the placing of a linked object, often an image, from one site in a web page belonging to a second site. The second site is said to have an inline link to the one where the object is located. It is used for such activities as linking images from personal home page storage into the online diary of the person controlling the personal home page.

There is no difference to a Web browser between a HTML reference to an image on the same site, and one on a different site. Both links would be written with the same HTML code. The ability to display content from one site within another was part of the original design of the Web's hypertext medium. The blurring of boundaries between sites, however, can lead also to other problems when it violates users' preconceived notions, as in the case of cross site scripting.

When a web site is visited, the browser first downloads the textual and style/layout content in the form of HTML and stylesheet files. These files contain <img> tags which supply URLs for images to display on the page. Normally, these URLs are relative URLs that refer to images on the same server, but HTML also permits absolute URLs referring to images on other servers. Thus, when a browser downloads an HTML page containing such an image, it will contact the remote server to request the image content from it.

This has sometimes been controversial because it is possible that the site where the object is stored and from which it is retrieved will not like the new placement or will consider it to be bandwidth theft. This term refers to the unauthorized use of someone else's bandwidth. Inline linking to an image stored on another site increases the bandwidth use of that site, even though their site is not being viewed in its intended form. Since bandwidth is a commodity, unauthorized use can increase the maintenance costs of the website hosting the image, hence the term bandwidth theft. As a result, some servers are programmed to use the HTTP referer to detect hot-linking, and return a condemnatory message (usually in the same format) in place of the expected image or media clip.

Some other forms of hotlinking also include video files, music (or mp3) files, animations (such as flash), and just about every other form of media.