A single-pixel GIF file set to a transparent status and thus invisible. Also known as a "transparent GIF," "1-by-1 GIF" and "clear GIF," it is is used as a tracking mechanism for Web pages to monitor a user's activity. See Web bug and GIF.
"invisible GIF." YourDictionary, n.d. Web. 17 August 2018. <http://www.yourdictionary.com/invisible-gif>.
invisible GIF. (n.d.). Retrieved August 17th, 2018, from http://www.yourdictionary.com/invisible-gif