The expression, inb4 is used as the abbreviation for the phrase “In Before”, meaning that a user on social media sites and especially on message boards is going to predict the response of another user in the discussion.
It is an especially prevalent slang expression on sites like Reddit, 4chan, as well as games, used to predict the plot twists of haunted house stories, anime plots, as well as the urban legend Man Door Hand Hook Car Door.
Although the exact origin of “inb4” is not known, it can be traced back to the /b/ board of 4chan, also known as the “random board”, where it started appearing in a larger number of posts and discussions during 2007.
By 2009, its prevalence had risen so significantly that it started appearing outside of 4chan, notably on Reddit, and due to the rising popularity of the expression, the first entry about “inb4” was uploaded to Urban Dictionary on January 9th, 2009.
Thanks to the widespread trolling on message- and image board sites, “inb4” spread fast like a copypasta, gaining a prominent position among internet slang expressions.
Its early days of only being used/known on the discussion board site 4chan quickly passed by and it has become a term used on most of social media, image sharing and video sharing websites.
“Inb4” became the go-to slang term online in any context, related to anticipation, prediction or Bait.