Seriously, this is just cool. Being able to take screenshots of the Webpage you are looking at without the need for cropping the rest of the image is a life saver.

People often take screenshots of web pages for miscellaneous reasons - when designing a page, debugging a web application, or even for graphical reference. Usually, though, only a portion of the screenshot is actually relevant to the user’s purpose, leading to a large portion of the image getting cropped. This can be time consuming, and annoying at times.

Snapper allows users to designate an area of a web page for a focused snapshot, cutting out the additional work needed for cropping unnecessary information…. Source: Firefox’s Snapper