Hotlinking
Hotlinking, also called direct linking or bandwidth theft, is when you post an image by using it’s URL/web-address from a site, server or hosting account that isn’t your own. For ex; instead of saving the image to your own computer and then uploading it to your own hosting account (such as Photobucket, ImageShack for example), you simply check the properties of the image and use the URL being used to display the image.
Bandwidth costs money. It’s also therefore limited in one way or another on every website. Data transfer occurs every time someone views an image, a webpage, or downloads a file from the website. When the bandwidth or datatransfer exceeds it’s allowed limit it will either result in:
1) the owner gets charged for the overage fees. Which could end up in the site shutting down if the owner feels he/she cannot pay the extra fee.
or
2) the site shuts down for the rest of the month/bandwidth period - which automatically robs everyone of access to the images at the site.
Another thing to keep in mind is that the owner of the site has the possibility of displacing the image you are hotlinking so that you might end up with images that say for ex; “I steal bandwidth”, “I’m a thief”, “I’m a stupid hotlinker” or just a really nasty image.
Another reason NOT to hotlink is getting reported to you webhost and possibility of having your site/account shut down.
AltLab has a really good explanation of what hotlinking is:
Bandwidth theft or “hotlinking” is direct linking to a website’s files (images, video, etc.). An example would be using an <IMG> tag to display a JPEG image you found on someone else’s web page so it will appear on your own site, journal, weblog, forum posting, etc.
HOW DO I KNOW I’M HOTLINKING?
[…] if you were to hotlink an image from an outside server
it might look like this:
<IMG src="http://notmysite.com/image.jpg" height="350" width="200">
/end quote
