The '6 Digit Codes' meme originates from the numerical indexing system used by the adult manga site nhentai. In anime and manga subcultures, these six-digit numbers became a shorthand for sharing specific content without directly linking to it, leading to the popular slang term 'sauce' (a play on 'source'). The meme often involves characters demanding 'the numbers' or reacting to infamous codes like '177013'. It serves as a cultural literacy test within the community, where knowing a specific set of numbers identifies one as an experienced internet user. Today, it is widely used across Discord, Reddit, and Twitter to ask for the origin of any anime-style image.