The Backrooms are an online urban legend originating from a creepypasta posted on a 2019 4chan thread. One of the most well-known examples of the Internet aesthetic of liminal spaces, which depicts usually busy locations as unnaturally empty, the Backrooms was first described as a maze of empty office rooms that can only be entered by "noclipping out of reality". As its popularity grew, internet users expanded upon the original concept by creating different levels and entities which inhabit the Backrooms. Fan-made video games, collaborative fiction wikis and YouTube videos have also been created: a series of horror shorts created by YouTuber Kane Parsons in 2022 is credited with popularizing Backrooms content on the mainstream internet.
Chroma key compositing, or chroma keying, is a special effects / post-production technique for compositing (layering) two images or video streams together based on color hues (chroma range). The technique has been used heavily in many fields to remove a background from the subject of a photo or video – particularly the newscasting, motion picture and videogame industries. A color range in the foreground footage is made transparent, allowing separately filmed background footage or a static image to be inserted into the scene. The chroma keying technique is commonly used in video production and post-production. This technique is also referred to as color keying, colour-separation overlay (CSO; primarily by the BBC), or by various terms for specific color-related variants such as green screen, and blue screen – chroma keying can be done with backgrounds of any color that are uniform and distinct, but green and blue backgrounds are more commonly used because they differ most distinctly in hue from most human skin colors. No part of the subject being filmed or photographed may duplicate the color used as the backing.